Blair is silent for fear of provoking captors. But he plans a robust defence of his stance

Tony Blair will make an uncompromising defence of his refusal to negotiate with the terrorists holding Ken Bigley in an attempt to convince the British people that he is right not to intervene directly.

The Prime Minister last night spoke to the Bigley family for a second time after reading a transcript of Mr Bigley's harrowing televised appeal to Mr Blair to save his life. His wife, Cherie, said: "Like everyone in Britain, my heart goes out to the Bigley family."

Mr Blair maintained his silence yesterday amid fears that any public comments could provoke the group holding the 62-year-old civil engineer to carry out its threat to kill him. Blair aides described the predicament of the Bigley family as "ghastly," but said the Prime Minister remained determined not to give in to the demands of the group.

When he explains his stance to the British people, Mr Blair is expected to argue that the terrible treatment of Mr Bigley and his family illustrates why the West must stand firm in the global war on terrorism. "It may help to bring home to people the wider struggle we are involved in," one Blair adviser said.

Another Blair aide said: "People in America realise it is not something born of intervention in Iraq but a battle against terrorism that must be fought over the long term. When Iraq has become a stable, democratic state, the terrorists will move in somewhere else."

However, some allies fear the Prime Minister may pay a political price for the hostage crisis, because Iraq is widely seen as "Blair's war". Ministers are worried that Iraq will overshadow next week's Labour conference in Brighton.

Senior Labour sources yesterday promised a "policy-rich" conference at which the party would set out a radical, forward-looking programme for a third term to improve the daily lives of "hard-working families who play by the rules".

The Labour leadership hopes to avoid a damaging showdown over Iraq on the floor of the conference, but the issue will dominate many fringe meetings. A foretaste of the debate comes today from Robin Cook, the former foreign secretary. Writing in The Independent, he rejects Mr Blair's attempt to present "the new conflict [in Iraq] as a titanic struggle with international terrorism". He says Mr Blair is "in denial" if he imagines he is in conflict with only a handful of psychopathic terrorists.

Mr Cook writes: "There were no international terrorists in Iraq until we invaded it. Judged by its contribution to combating international terrorism, the occupation of Iraq has been a spectacular, grotesque own goal."

Peter Kilfoyle, Mr Bigley's local MP and a former defence minister, said: "There is going to be a backlash at the party conference. I have always said it was mistake to get involved in Bush's policy. Tony Blair has got to distance himself from Bush."

Michael Meacher, the former environment minister, called for a fresh Commons vote on the "second war'' for Iraq. "It is an unspeakably awful situation. I think it is doing a great deal of damage to Tony Blair. Britain should distance itself from America. We should withdraw from Iraq as soon as we feasibly can after the elections," he said.

But Mr Blair won strong support for his stance yesterday from Michael Howard, the Tory leader, who said the Government was "right that we can't give in to people who behave in this barbaric fashion". He told BBC Radio 4: "I feel desperately for Ken Bigley and his family. They must be going through the throes of such despair that the rest of us really can't begin to understand. And I feel for Mr Blair too, who is in the most unenviable predicament."