In an open letter published in The Guardian, Gro Brundtland - alongside other senior European statesmen and women - has called for renewed urgency in tackling problems of nuclear proliferation.

The recently signed arms control treaty between the United States and Russia (Start) brings welcome reductions in deployed nuclear warheads and an agreed ceiling on the number of delivery vehicles that each side may possess. We applaud the new agreement and the acts of political leadership required in both countries to bring it about. The breakthrough is all the more welcome, coming just before both the Washington summit on nuclear security and the review conference of the non-proliferation treaty (NPT). Across Europe, and at this moment of diplomatic opportunity, we have joined together to declare our unequivocal support for President Obama's vision of a world without nuclear weapons, to declare our desire to re-set the security relationship between Europe, the US and Russia, and to show strong European support for the measures necessary to deliver these goals.

Let no one doubt the importance of this endeavour. The risks of proliferation are growing. India, Israel and Pakistan have already entered the nuclear club. If Iran gets the bomb, others certainly will follow. We know that terrorist groups want to acquire nuclear materials, making the security of those materials an issue of truly global significance. Nuclear armed states inside the NPT have not been disarming fast enough, straining the confidence of their non-nuclear partners in the credibility of the NPT grand bargain. Without further action, there is a real danger that the world will be overwhelmed by proliferation risks and incidents of nuclear weapons use, with all their catastrophic consequences.

The strategic implications of this are profound. Nuclear deterrence is a far less persuasive strategic response to a world of potential regional nuclear arms races and nuclear terrorism than it was to the cold war.

The circumstances of today require a shift in thinking. We must, through further multilateral agreement, reduce the role and the number of nuclear weapons in the world, deepen confidence in the non-proliferation regime, and improve the security of existing nuclear weapons and materials. We must achieve these goals while at the same time helping those countries that wish to go down the civil nuclear energy route do so safely.

The practical steps necessary to achieve our goals are clear. In Washington, we must demonstrate wider international ownership of the issue of nuclear security. This is not just a concern for those fearing a nuclear terrorist attack. Any major nuclear security incident anywhere is likely to derail the civil nuclear renaissance everywhere. Regardless of whether we as individuals support the idea of more nuclear power, this may ultimately undermine global attempts to meet the challenge of climate change, an outcome we all have a stake in avoiding.

The Washington summit also must agree practical action on programmes to control and destroy nuclear materials and ready-made weapons within four years; and participants must agree to rationalise the many complex overlapping international conventions, initiatives and resolutions that are the current institutional architecture aimed at addressing this issue.

In May, at the NPT review conference in New York, the treaty, for 40 years the foundation of counter-proliferation efforts, must be overhauled and reinforced. All signatory nations should accept the strengthened monitoring provisions of the additional protocol. The IAEA needs that strengthened inspection power if it is to provide effective monitoring of declared and undeclared nuclear material and activities. Nations wishing to develop a civil nuclear capability must first agree to proper verification procedures and unimpeded access for the IAEA.

Progress of this nature will not be possible without a credible process for nuclear disarmament. Beyond Start follow-on we need urgent and more radical initiatives from the nuclear weapons states. Increasingly it is becoming more challenging to explain why some countries should have, and others should not be allowed to possess nuclear weapons.

All nuclear weapons, including tactical ones, must be included in disarmament talks. Where this necessitates discussion of conventional force imbalances, these too must be included. States that now possess nuclear weapons must work together to reduce their importance to national and international security.

The establishment of nuclear free zones in Latin America, sub-Saharan Africa and central Asia is very encouraging. By the end of the NPT review conference there must be a credible process for the discussion of a weapons of mass destruction free zone in the Middle East.

After May, attention must also return to other issues. The countries that have not yet ratified the comprehensive test ban treaty including the US, China, Israel, Pakistan, India and North Korea should do so urgently, allowing it to come into force. The stalemate in the Geneva disarmament conference on a fissile material cut-off treaty must also be overcome. We need a treaty-sanctioned prohibition of the production of the basic materials required to manufacture nuclear explosive devices.

Europe, through Nato, is central to the security relationship with Russia and can influence it through Nato diplomacy and the ongoing revision of Nato's strategic concept. The UK and France, working with other nuclear weapons states, can play their full part in discussions on disarmament, and in efforts to implement any internationally agreed and verifiable reductions in warhead numbers. In addition to that leadership Europe is a key player in civil nuclear power and nuclear security.

In short, Europe can and must play a vital role in building the co-operation necessary for meeting the global nuclear challenge. All our futures depend on it.

Signed:

Kåre Willoch, former prime minister of Norway

Kjell Magne Bondevik, former prime minister of Norway

Oddvar Nordli, former prime minister of Norway

Dr Gro Harlem Brundtland, former prime minister of Norway

Thorvald Stoltenberg, former minister of defence and minister of foreign affairs of Norway

Wlodzimierz Cimoszewicz, former prime minister and foreign minister of Poland

Ruud Lubbers, former prime minister of the Netherlands

Jean-Luc Dehaene, former prime minister of Belgium and current MEP

Guy Verhofstadt, former prime minister of Belgium and current MEP,

Lord Geoffrey Howe of Aberavon, former British deputy prime minister, chancellor of the exchequer and foreign secretary

Laurens Jan Brinkhorst, former deputy prime minister and minister of economic affairs of the Netherlands

Jan Kavan, former deputy prime minister and foreign minister of the Czech Republic

Volker Rühe, former defence minister of Germany

Hans Blix, former minister for foreign affairs of Sweden

Wolfgang Ischinger, former deputy foreign minister of Germany

General Bernard Norlain, former French general, former commander of the French tactical air force and military counsellor to the prime minister

Lord George Robertson of Port Ellen, former British defence secretary and secretary-general of Nato

Sir Malcolm Rifkind, former British defence secretary and foreign secretary

Admiral the Lord Michael Boyce, former British Chief of the defence staff

Lord Charles Guthrie of Craigiebank, former British chief of the defence staff

Lord Douglas Hurd of Westwell, former British foreign secretary

Margaret Beckett, former British foreign secretary

Des Browne, former British defence secretary

Lord Tom King of Bridgwater, former British defence secretary

Louis Michel MEP, former minister for foreign affairs of Belgium

Mogens Lykketoft MP, former minister for foreign affairs of Denmark

Niels Helveg Petersen MP, former minister for foreign affairs of Denmark

Uffe Ellemann-Jensen, former minister for foreign affairs of Denmark

Frits Korthals Altes, former president of the senate and minister of justice of the Netherlands

Michael Ancram, former British shadow foreign secretary and shadow defence secretary

Dr John Reid, former British defence secretary

Sir Menzies Campbell, former British leader of the Liberal Democrat party and Liberal Democrat shadow foreign secretary

Shirley Williams (Baroness Williams of Crosby) former adviser on nuclear proliferation to British prime minister Gordon Brown

Charles Clarke, former British home secretary

James Arbuthnot, former British chair of the defence select committee

Adam Ingram, former British defence minister of state (armed forces)

Professor Ivo Šlaus, former Croatian MP, former member of foreign affairs committee and current emeritus professor of physics

Francesco Calogero, Italian theoretical physicist & former secretary-general of Pugwash

Giorgio La Malfa MP, former Italian minister of European affairs

Federica On. Mogherini Rebesani, member of the Italian parliament