Mr Cameron said time management was important

It would still be possible to spend time with his family "if you arrange your diary properly", he told ITV1's This Morning show.

Mr Cameron also insisted he would find time to bath his three children, which he still did at least once a week as leader of the opposition.

It was "really important" to maintain family life, he added.

'Clear rules'

Mr Cameron's third child, Arthur, was born last year, after he had become Conservative leader.

Prime Minister Tony Blair became a father for the fourth time in 2000 while in Downing Street.

Mr Cameron said: "I think if you have a strong team, good people working with you and you set clear rules about, you know, you can't work 24 hours a day.

"What I try and do, for instance, tonight I'm going to leave the office, I think, about 6 o'clock and I'm going to try and get home for bathtime.

"Now I try and do that once a week. I think that's really important."

Asked whether he would be able to keep this up in Downing Street, Mr Cameron said: "Yes, I think if you arrange your diary properly, if you make sure you fit the meetings in when they are necessary.

"In modern-day communications, we've all got Blackberries and pagers and phones - anyone can get hold of you if there's something that needs to be done.

"I'm convinced you can be a good party leader and a good dad."