MARGARET BECKETT, the foreign secretary, has reopened the controversy over Britain’s nuclear deterrent by calling for a public debate on whether the country still needs Trident missiles.

In an interview with The Sunday Times she points out that the “security situation today is very, very different” from the end of the cold war. She says that “all of us as a country”, not just the government, should be able to question the policy.

Tony Blair has been committed to the independent nuclear deterrent, saying it is “an essential part” of defending the country. In addition Gordon Brown, whom Beckett today publicly backs as his successor, has signalled his commitment to replacing Trident.

In the interview, Beckett also becomes the first member of the government to express “regrets” over the Iraq war, despite Blair’s explicit refusal to do the same.

The foreign secretary would not contradict comments by General Sir Richard Dannatt, the head of the army, who argued that the presence of British troops in parts of Iraq was jeopardising security. Beckett admits there are “particular difficulties and problems”.

Her call for a widespread debate on the nuclear issue, which split Labour in the 1980s, may have wider political reverberations. Beckett says that the government will publish a white paper shortly. “I do think there is real merit in publishing the white paper because I think it would be a very good thing for all of us as a country to think carefully about what the situation of today is,” she says.

“The nature and shape of the nuclear deterrent we have and are maintaining and keeping up to date was dictated in the cold war circumstances of decades ago. The security situation today across the world is very, very different.

“But whether it is less dangerous, and what decisions that leads you to, is quite another matter. And I think that is something people deserve to have laid out before them and to be able to think about it for themselves.”

Referring to the need for a public debate on the nuclear deterrent, the foreign secretary says, “I’m sure people will question whether we need one or not”, adding: “Obviously whenever you look at these issues the question is: do we go on with this? And, if we do, in what way? And why? And what are the issues the government is taking into account when they are considering what their decision should be?”

Her comments are likely to be welcomed by Labour MPs who have been demanding a vote on the issue. Sceptics argue that nuclear weapons are useless against international terrorism and bemoan the estimated £20 billion replacement costs.

Beckett acknowledges that Labour’s general election manifesto pledged to retain the deterrent. But few MPs doubted there was ever a question of the Trident submarine system not continuing to the end of its expected lifespan of another 20 years, and the issue the government now faces is what will happen beyond that.

The issue is set to return to the agenda in the coming weeks after the prime minister told parliament in the summer that a decision would be taken “this year”.

A cabinet discussion is expected soon, followed by the publication of the white paper. The prime minister is under pressure from Labour MPs to spell out the options in his final months in office.

Many were dismayed that motions on the issue were blocked at the party conference last month. More than 120 MPs have already signed a motion tabled by Michael Meacher, the former environment minister, demanding a vote on Trident. Some fear that Blair will renege on his pledge to have a parliamentary debate. He has refused to commit himself to giving MPs the final say with a vote on the issue.

Clare Short, the former international development secretary, cited the lack of debate over Trident as one of the reasons that led her to leave the Labour party this month.