A 57-year-old woman says she was left feeling "past it" after being refused a place in the audience for a televised debate with Gordon Brown, David Cameron and Nick Clegg because she was too old.

But the company selecting the audience for the debate denies it is excluding people because of their age.

Researchers knocked on Marilyn Williams' door asking if she would be interested in attending the leaders' debate which will be held in Bristol once the date of the general election is announced.

Mrs Williams, who always makes the trip to the ballot box on polling day, said yes and the pair started filling out the forms.

But when she was asked her age, she claims the researcher apologised and told her she was too old to take part.

Mrs Williams, of Hawkesbury Upton near Badminton, told the Evening Post: "A woman came to the door, showed me her badge and told me she was looking for audience members for the debate.

"I have always been interested in politics so I said yes and she began filling in the form with my details. When she asked me how old I was, I told her and she said, 'I'm ever so sorry but the cut off is 54, is there anybody younger in the house?'.

"I was flabbergasted. I am officially past it. It was a bit of an insult. I don't feel like an old person,

I foster teenage children – but I felt like an old dodderer who should be sitting in an armchair.

"I have always voted, I think it should be illegal not to vote. Who you vote for is your own business, but if you don't vote, don't moan. I would have liked to have been able to go."

The three main party leaders agreed to take part in the first live general election televised debates back in December and ITV, Sky News and the BBC drew lots.

Last week it was revealed Sky had been assigned the second debate which will be staged in Bristol. It will be hosted by Adam Boulton and focus on international affairs.

Members of the audience will be able to put questions to Prime Minister Gordon Brown, Conservative leader David Cameron and Liberal Democrat leader Nick Clegg directly and viewers will also be able to submit their own questions by email in advance.

The broadcasters jointly appointed the market research company ICM to recruit an audience with a broad cross-section of views.

A spokesman for ICM insisted it had no age cut off point and had already recruited one audience member who was 80 years old.

He added: "It is nonsense to suggest we have an age limit. We want a balanced audience. It is blatantly and completely wrong.

"We are not going to be excluding anyone on the basis of age. It is completely impossible.

The ICM spokesman refused to explain the criteria the company used when recruiting audience members but insisted they were seeking a representative mix.

The only possible reason for excluding anyone on the basis of age was if the target number of people in a particular category had been met, but he added the recruitment was in its early stages so that was not possible.