A senior Conservative is to go on TV with the sensational claim that David Cameron's wife Samantha has voted Labour in the past and could back Gordon Brown in this year's general election.

But arts spokesman Ed Vaizey, a friend of Cameron's from Oxford University who is a member of the "Notting Hill set", admitted he has "no justification" for the claim and is "very embarrassed" to have said it.

In a documentary, Cameron Uncovered, to be broadcast on Channel 4 on Monday, Mr Vaizey tells interviewer Andrew Rawnsley that he will be "in a whole lot of trouble" for making the suggestion.

But he goes on to add that Mrs Cameron "might have voted for Blair" and says: "She would be going into this poll thinking, 'Is Cameron the real deal or should I stick with Brown?'"

Meanwhile, another member of the Camerons' social circle claimed Samantha was behind the Tory leader's famous comment - seen as an attempt to distance himself from the legacy of Margaret Thatcher - that "there is such a thing as society, it's just not the same thing as the state".

Mr Cameron's former speech writer Danny Kruger says he understands the phrase was coined by Samantha when she heard him speaking and said: "What you're actually saying is this..."

In the programme, Mr Vaizey quickly adds that his comments are "conjecture". And he later told the Mail on Sunday: "The point I was trying to get across is Sam is a professional woman who is not tribal about her politics and likes strong leadership. I haven't a clue whether she voted for Blair and I would be very surprised if she did."

A source close to Mr Cameron told the Press Association: "She has never voted Labour and never will. Complete rubbish."

And Mr Vaizey - whose Wantage constituency neighbours Mr Cameron's seat - himself later released a statement saying: "I am very embarrassed by this. I had no justification for what I said.

"The only thing I do know from seeing David and Sam for many years is that Sam worked night and day on David's campaign in 1997 in Stafford and, as she said, has never voted Labour."

© Press Association 2010