Rory Bremner has tricked Margaret Beckett into revealing political secrets after posing as Gordon Brown on the phone.

The impressionist was so convincing that the Foreign Secretary was happy to freely criticise Cabinet colleagues, convinced she was talking to the Chancellor.

Bremner taped the five-minute conversation for his Channel 4 show, but producers decided not to air it for fear it broke broadcasting guidelines.

During the conversation, she criticised Health Secretary Patricia Hewitt and discussed the chance of Blairites Alan Milburn and Stephen Byers making a return to the top of the party.

She also claimed she would be able to solve climate change problems, grandly claiming: ‘The whole of Europe is saying, “Leave that to Margaret.” ’

When discussing her colleagues’ chances, Beckett at one point said: ‘Being perfectly honest, Gordon, and I wouldn't say this to anybody else’

Bremner said: ‘I was amazed by the factionalism [the conversation] exposed, She seemed pleased to be rung and was almost quite coquettish, saying at one point "I wouldn't tell this to anyone else".'

The call was made on the eve of the 2005 General Election, but Beckett only became aware that she had been duped last night when journalists got hold of the story.

And even now, she insists she has no recollection of the talking to the bogus Brown and said the call was an 'unprincipled and unpleasant breach of privacy'.

She said: ‘‘I have never given my phone number to Rory Bremner nor knowingly had a conversation with him. Never have I made a practice of discussing colleagues with journalists other than in positive terms.'