The humiliation of a Premier - video report

The day Brown didn't use his loaf

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The Prime Minister spent 40 minutes at Gillian Duffy's house to say sorry after a microphone recorded him in his car branding the encounter with her on the street in Rochdale a "disaster".

And with the party's bid for a fourth term in office last night in turmoil he apologised to Labour activists in an email as he admitted the incident will have impacted on campaigning.

With Labour already trailing in third behind the Liberal Democrats in some opinion polls just seven days before the election, the incident threw Mr Brown's campaign – and hopes of defending a string of vulnerable Yorkshire seats – off track just as he had been planning to prepare for tonight's final debate between the three party leaders.

Mr Brown said he was "mortified" and insisted he was a "penitent sinner" after meeting Mrs Duffy again. Last night he said he had hurt "the kind of person I came into politics to serve".

In his email to Labour members Mr Brown said he profoundly regretted his comments, adding: "As you may know, I have apologised to Mrs Duffy for remarks I made in the back of the car after meeting her on the campaign trail in Rochdale today. I would also like to apologise to you.

"I know how hard you all work to fight for me and the Labour Party, and to ensure we get our case over to the public.

"So when the mistake I made today has so dominated the news, doubtless with some impact on your own campaigning activities, I want you to know I doubly appreciate the efforts you make."

The incident – which comes with Mr Brown under pressure to meet more ordinary people rather than seeing party audiences – followed a visit by Mr Brown to a community payback scheme in Rochdale.

Lifelong Labour voter Mrs Duffy chanced upon his appearance but took advantage to take the Prime Minister to task over issues including the national debt, taxes, student financing and immigration.

The conversation appeared to end cordially with Mr Brown declaring "it's very nice to see you".

Failing to remove his microphone before getting into the car, he told Justin Forsyth, his director of strategic communications: "That was a disaster – they should never have put me with that woman."

Asked what she had said, Mr Brown added: "Everything, she was just a bigoted woman."

The incident was picked up by broadcasters and within minutes was being played live on TV much to Mr Brown's humiliation and Mrs Duffy's anger, describing the comments as "very upsetting" and saying she was "not bothered" whether he won the election or not.

Whisked away to a radio interview, Mr Brown was pictured with his head in his hands as his conversation was played back to him and he issued a grovelling apology.

He later travelled to Mrs Duffy's house where he was inside for 40 minutes before emerging to speak to journalists.

"I have given her my sincere apologies," he said.

"I misunderstood what she said. She has accepted that there was a misunderstanding and she has accepted my apology. If you like, I am a penitent sinner."

Mrs Duffy remained silent after the meeting but last night her niece – also called Gillian – claimed her aunt was unlikely to accept the apology.

"It's disgraceful," she said. "He's just shown his true colours. He's always trying to pretend to be so nice and in touch with the people but he's obviously not. I can see it anyway."

While Mr Brown's campaign was imploding, Tory leader David Cameron made his fourth visit of the campaign to Yorkshire as he turned his attention to ousting Schools Secretary Ed Balls in Morley and Outwood.

He toured the Coca Cola distribution centre at Wakefield Industrial Park before being quizzed by workers where he defended Tory plans for the economy after criticism from a think-tank that all three parties were leaving voters in the dark about the full scale of tax and spending plans.

SNP FAILS TO BLOCK LEADERS'TV DEBATE

The final leadership TV debate will take place as planned tonight after the Scottish Nationalists failed in a last-ditch attempt to block the TV clash.

The SNP mounted a legal challenge at the Court of Session in Edinburgh, arguing it should not be screened in Scotland if their party was not included.

But the court dismissed the claim and the debate format will remain as before, the parties this week tackling the economy, following on from the previous clashes over domestic and foreign affairs.

Gordon Brown and David Cameron will be desperate to make up ground lost to the Liberal Democrats, who have led many polls following party leader Nick Clegg's first two performances.