A tearful David Blunkett tonight said that his political fate was sealed when he decided three months ago to put his duties as a father above his political career.

In television interviews he claimed that his over-riding motive had been his desire to hold his youngest son in his arms once more, as he had when the child was a baby.

Mr Blunkett - who already has three sons by his marriage, which ended 16 years ago - maintains that he is also the father of the first child of his former mistress, Kimberley Quinn. He has taken legal action in the family courts to gain access to the child.

"What I didn't realise was that the decision I took in September to see my youngest son again and to hold him as I did as a baby... would heap this on my head," said Mr Blunkett.

His face reddened and his mouth began to work as he continued: "I'm very sad about it."

He condemned the people who had "spread lies" about him, claiming that he was trying to obtain custody of the baby when he only wanted to see the child again.

"I would not bring that down on my head, or on my little boy's head," he continued, tears in his eyes. "There are people whose consciences should be examined tonight, and the consequences of what they have done to that little boy's future, and I hope that they think about it."

In the last month, Mr Blunkett's probity has been called into doubt by a barrage of allegations that he fast-tracked visa applications for Mrs Quinn's Filipina nanny, as well as misusing his official car to ferry his lover about and giving her official parliamentary rail permits worth £180.

He admitted the rail permits and repaid the money, but has always denied interfering in Leoncia Casalme's visa applications - until it emerged tonight that there had been an exchange of e-mails between his office and the immigration service about Ms Casalme.

Mr Blunkett quit and immediately embarked on a round of television interviews to minimise the political damage to Tony Blair, who has backed him throughout the crisis, and to his own hopes of resurrecting his career in the future.

He promised that he would be on the election campaign trail with the Prime Minister, who he said was a loyal friend and a better man than many people in Britain realised.

Questioned on the circumstances of his downfall, the Home Secretary seemed to imply that an official letter from the Immigration and Nationality Directorate about Ms Casalme's case had found its way into his work tray accidentally, and had been acted upon by his officials without his knowledge.

He implied that Ms Casalme's case had raised general policy issues about the backlog in obtaining visas that he was already examining in his capacity as Home Secretary.

"I knew we had to take action about the backlog exercise as we were about to charge people £150 to have their visa renewed. But I had not realised that I had put that letter in with my overnight work and it was acted upon."

Even this was not necessarily unusual, Mr Blunkett claimed. "I do use individual cases to get to grips with policy," he explained.

And he defended his impulse to help Mrs Quinn to overcome the nanny's visa problems. He said: "I would always do a favour (for a friend), without embarrassing or putting at risk my propriety or using my public office for personal gain.

"I think a human being that sends someone away and says they can't help isn't a human being at all."

Admitting that everything had gone wrong for him personally and professionally in the course of three short months, he went on to defend his actions.

He said: "Looking back, I can see the points in my life when it could all have been different. But in September, when I was given the option of walking into the sunset and out of that little boy's life, I was right not to.

"What kind of man would actually put their career, their public persona, before doing what a decent human being would want to? I don't think people want politicians like that, and if they do, they don't want me."

Mr Blunkett brushed aside the implication that he was resigning because there was any truth in the more lurid allegations that he had misused his power, including today's claims about a visa for Austria. He said: "I have read such terrible garbage in the last few weeks. I have read allegations that I used public funds for legal bills in my efforts to see my youngest son.

"There have been the most terrible allegations, none of which are true except for the ones that I have publicly acknowledged are true."

Explore UK News

• Crime News

• Education News

• Health News

• Scotland News

Times Recommends

• A vicar’s wife: ‘There is no one to fight for us’
• Every little helps at the supermarket
• Ugg or Fitflop? The battle of the boots