Former Home Secretary Charles Clarke has criticised Tony Blair's foreign policy, saying that good intentions have "turned to dust".
Mr Clarke said Mr Blair did not want to 'rock the boat'
In an article for the New Statesman, he attacks his ex-boss's record on Europe, "ethical" foreign policy and nuclear non-proliferation.
Mr Clarke said Mr Blair was "hasty" in wanting to replace Trident missiles.
He also accused the prime minister of having a "desire not to rock the boat" on arms sales to Saudi Arabia.
However, Mr Clarke cautioned against the assumption that matters would improve under the leadership of Gordon Brown.
He argued the chancellor was as responsible as Mr Blair for the development of foreign policy.
He said: "The Blair premiership is a classic illustration of the potential for good intentions to turn to dust.
"The Britain which was to be at 'the heart of Europe' has failed to face its Euro-demons and is now more remote from the centre of European power than ever.
"An 'ethical foreign policy' has given way to a desire not to rock the boat of arms sales to Saudi Arabia.
"And a commitment to nuclear non-proliferation has yielded to an over-hasty and ill-considered determination to renew Trident, whatever the future security threats.
"These have been the approaches of the whole government, with the chancellor bearing as much responsibility as the prime minister - indeed, in some areas more."
Mr Clarke - who has said he expects to vote for Mr Brown in any leadership contest, despite earlier criticisms of his style - questioned whether the chancellor would be able to provide the "committed international engagement" required.
Last year, Mr Clarke accused Mr Brown of "absolutely stupid behaviour" during a row over Mr Blair's leadership.
He said the chancellor was a "control freak", who lacked confidence and could not manage people in a "collegiate" way.
But he later apologised for his comments.