The official, speaking on condition of anonymity, said the British embassy had informed all airlines in an email on Friday not to allow the couple to board flights to Britain.

'The British embassy sent an email message to all airlines operating from Bangkok on Friday that the British authorities had revoked the visa for Thaksin and Pojaman,' he said.

'It's (the email is) general practice for all airlines, so no airline can take them on board to England from any port,' he added.

'The United Kingdom Border Agency has revoked the UK visas held by the following Thai nationals: Thaksin Shinawatra, Thai Passport Number D215863; Potjaman Shinawatra, Thai Passport Number D206635.

'The UK visas contained in the passports of the individuals listed above are no longer valid for travel. Airlines are advised not to carry these passengers to the UK.'

Thaksin, ousted in a 2006 coup, fled to Britain in early August and has since been sentenced in absentia to two years in prison for corruption.

His exact whereabouts on Saturday were unknown, but local media reported he was travelling from China to the Philippines.

Thaksin's Thailand-based spokesman said he could not confirm the report.

'What I can verify is that Thaksin has not received any document from the British authorities concerning this issue.... But if it's true Thaksin can clarify the matter,' said Phonthep Thepkanjana.

According to the Bangkok Post, a 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.