Ex-president of the Soviet Union Mikhail Gorbachev has joined calls for Tony Blair to abandon plans to replace Britain's Trident nuclear missiles.
Mr Gorbachev is 'astonished' by UK's nuclear policy
He accused Mr Blair of ignoring the spirit of the treaties which ended the Cold War nuclear stand-off.
In a letter to The Times, he said the "responsible course of action" would be to delay a decision until the next non-proliferation talks in 2010.
MPs are due to debate replacing Trident - at cost of up to £20bn - next week.
The crucial commons vote will be on whether to acquire a new generation of nuclear submarines and Trident missiles, maintaining the deterrent into the middle of the century.
The government is expected to win support for replacing Trident, with Conservative backing.
The Liberal Democrats, who also favour delaying a decision on replacing Trident, will vote against renewing the government's policy.
At the weekend, Lib Dem leader Sir Menzies Campbell saw off a challenge from unilateralists in his own party at its spring conference in Harrogate.
Sir Menzies favours halving the number of warheads stockpiled by the UK but delaying a decision on replacing them until 2014 in order to give the UK leverage in non-proliferation talks.
Mr Gorbachev, whose glasnost, or openness, policy was credited with hastening the end of the Cold War, and the break-up of the Soviet Union, also urged the British government to delay a decision on Trident.
In his letter to The Times, Mr Gorbachev pointed to a warning by the head of the International Atomic Energy Agency, Mohamed ElBaradei, that many countries were already reluctant to ratify an additional protocol to the Non-Proliferation Treaty imposing more effective nuclear controls.
"Under such circumstances the UK government's rush to deploy nuclear missiles whose service life would extend until 2050 is, to say the least, astonishing," he wrote.
He went on: "The Treaty on Non-Proliferation of Nuclear Weapons commits the nuclear powers to effective measures of nuclear disarmament.
"In fact, the entire structure of that treaty, which is already under considerable strain, rests on that commitment. "The decision to deploy new nuclear missiles would be in contradiction to the spirit of the agreements that helped to end the Cold War."