The British government is reported to have revoked the visas for convicted former prime minister Thaksin Shinawatra and his wife, Khunying Potjaman, effectively banning them from entering Britain on their Thai passports, a reliable airline source said last night.

The source said the notification letter on the visas being revoked was circulated by e-mail to airlines which are members of the Airport Operations Committee yesterday.

The source said the letter was sent by Andy Gray, an official at the UK Border Agency who is in charge of immigration at the British embassy in Thailand.

The letter made clear that the visas issued for Thaksin and Khunying Potjaman were now invalid and the couple should be prevented from boarding planes to Britain, the source said.

Thaksin's visa is stamped in his Thai passport, number D215863. Khunying Potjaman's passport number is D206635, the source added.

Another source said Thaksin is now in China after calling his supporters in the United Front of Democracy against Dictatorship (UDD) at the Rajamangala stadium on Nov 1 from Hong Kong.

The whereabouts of his wife are unclear. It is not known whether she accompanied her husband from London to Hong Kong and then China.

Thaksin and Khunying Potjaman, along with their family, have spent most of their time in London after fleeing justice in Thailand.

Another source close to Thaksin said the former prime minister and his wife have been granted honorary citizenship of the Bahamas and they can travel on Bahamian passports.

Meanwhile, Maj-Gen Chamlong Srimuang, one of the core leaders of the People's Alliance for Democracy (PAD), does not believe Privy Council president Prem Tinsulanonda will step in to mediate in peace talks between the PAD and the government.

He said Gen Prem may not take up the role of mediator because pro-government groups, especially the UDD, which may be approached to enter the dialogue, have constantly criticised Gen Prem.

Last year, the UDD staged an anti-coup rally outside Gen Prem's Si Sao Thewes residence. The protest culminated in violent clashes between demonstrators and police.

UDD leaders such as Veera Musikhapong and Jakrapob Penkair have strongly criticised Gen Prem for allegedly being behind the coup d'etat which toppled Thaksin's government. They also demanded Gen Prem resign as Privy Council president.

Maj-Gen Chamlong said Gen Prem's involvement as a mediator in the conflict could only be detrimental to his own reputation.

However, Maj-Gen Chamlong stressed the alliance had never closed the door on peace negotiations.

Maj-Gen Chamlong said peace talks must involve only the PAD and the government.

The mediator may be one person or a group of people and they must be acceptable to both sides, Maj-Gen Chamlong said.

The government may also contact the PAD directly to initiate the peace process.

But Maj-Gen Chamlong confirmed the alliance's stance against the government's bid to amend the constitution.

Defence permanent secretary Apichart Penkitti agreed with the calls for the two opposing sides to resolve their dispute through dialogue.

"I think dialogue should be the first option. This option should be taken if there are no other better ways out," Gen Apichart said.