The union said it had discovered that Thais had to listen to "illegal" community radio stations to find out what was going on at the anti-government protests, it said in a statement.

It quoted Senator Somkiat Onwimon saying people would previously have tuned into the BBC for the latest news.

Last week the British House of Commons debated a motion to resume the Thai-language service, which was one of 10 BBC services cut by the Foreign Office at the beginning of this year.

The union's general secretary, Jeremy Dear, warned that the cuts to these services would mean the loss of a vital source of information within countries such as Thailand where the World Service had many loyal listeners. "This blocks the access people have to the truth and as a result strikes at the organs of democracy. The government must rethink its decision," he said.

Labour MP John Grogan, who raised the issue during last week's House meeting, said he would write to the director of the BBC World Service tomorrow, urging him to re-open the Thai service to cover the political turmoil.

In the House debate, Grogan pointed to the need for an alternative channel of information and opinion on the demonstrations, and the debate about democracy in Thailand.

"For the past 60 years, the BBC World Service Thai service, almost uninterrupted, has been adding to that debate and, in the traditional role of the BBC, has been helping to keep the domestic broadcasters and media honest," he said.

The British National Union of Journalists has 35,000 members in Britain and Ireland.