Yasser Arafat, the Palestinian leader, has pledged to help in efforts to seek the release of Ken Bigley, the British hostage held captive in Iraq.
Paul Bigley, the hostage's brother, said Mr Arafat had asked a Palestinian minister, who had spent many years in Iraq, to help free the 62-year-old from his captors in Iraq "in every way possible".
Mr Bigley told the ITV News Channel it was "fantastic news," which had been relayed to him by the representative of the Palestinian Authority in Ireland. He contrasted it with the efforts of Tony Blair, who he accused of not doing enough.
In a series of interviews, Paul Bigley said that, while he did not expect governments to get into negotiations with terrorists, he believed more could have been done.
He told BBC Breakfast News that the Prime Minister was a "gentleman and a statesman" but repeated his calls for him to resign: "I think his sell-by date has gone and he has to go. There has to be a change of face, a change of policy, a change of dialogue."
Mr Bigley, who is based in Amsterdam, went on: "We have got to stop these people doing these things ... people are losing their lives."
He reiterated his plea for the Government to "open a dialogue" of some kind to the terrorists, but accepted it should not negotiate. He said: "I never would and never will request that you negotiate with bad people."
Mr Bigley, who said he had received news on Sunday night that suggested his brother was still alive, added: "I truly believe my brother is alive. It came through the grapevine. I know it sounds silly but that's the way it works over there."
He repeated his accusation that the President George Bush had "blocked" the release of two female prisoners in Iraq, whose freedom has been demanded by the kidnappers.
Mr Arafat is the most high-profile figure in the Arab or Muslim world to attempt to mediate in the crisis. The Foreign Office said yesterday that it was investigating claims by Yasser al-Serri, an activist who runs the Islamic Observation Centre in London, that he had received news that Mr Bigley was alive via intermediaries in Iraq after a plea for his release. A Foreign Office spokesman said: "We have seen the report and we are currently trying to establish how credible it is."
Mr Serri is a controversial figure and, in 2002, successfully fought extradition to the US, which claimed he has been involved in fundingal-Qa'ida. His appeal to the kidnappers, believed to be a group headed by Abu Musab al-Zarqawi, one of the world's most wanted men, was based on Islamic law.
Two leading British Muslims, who had spent the weekend meeting the Iraqi President and religious leaders to try to secure Mr Bigley's release, were returning home last night from Baghdad. Daud Abdullah and Musharraf Hussain said they were encouraged by promises that all was being done to try and open a dialogue with the captors.
Ken Bigley was snatched 11 days ago from his home in the al-Mansour district of Baghdad along with two American colleagues. Both the Americans have been beheaded.
The British embassy has distributed 50,000 leaflets containing pleas from the Bigley family and placed the appeal in a city newspaper.
The Chancelor, Gordon Brown, told the Labour conference: "The thoughts of everyone at this conference are with Ken Bigley and every member of his brave family."
At the Bigley home in Liverpool, bouquets of flowers and cards from sympathisers continued to arrive.