Close observers of the political scene had noticed a change in the Conservative leader's appearance this week.

Just as the Conservative Party had moved from right to left under David Cameron, so has the parting in the hair over Cameron.

Some thought the follicle shift might be a bid for women voters. Rodger Craig, a celebrity hairdresser, told BBC Radio it was feminine to part your hair on the left, implying Cameron had decided to recast himself as metrosexual man. Others, who observed Cameron from the gallery overlooking the Commons debating chamber, thought they had detected a bald spot emerging on the Tory leader's crown, and speculated that the change of hairstyle was an attempt to hide this symptom of ageing.

Yesterday, Conservative Party officials tried to put an end to all such hair-splitting.

They said that it was the local hairdresser near Cameron's London home who advised him that his hair was parted on the wrong side.

Cameron, who normally goes to a hairdresser on the ground floor of the House of Commons, took his children to the Hair and Tanning Rooms in St Helens Gardens.

"He decided to have his hair cut there as well, and the barber said, 'You have got your parting on the wrong side', " a Conservative spokesman said. "He decided to take his advice. I think he likes it, so he's likely to stick with it."

Tony Tahir, 65, has been a hairdresser for 45 years, and has run the Hair and Tanning Rooms with his wife Sandra for the past 26 years. He said that David Cameron had been one of his customers for the past 18 months.

"We discussed the change in parting together, and came to an agreement that he should try it because it is the way his hair naturally grows - and it has been a great success, " Tahir said. "You shouldn't go against the cross of the hair. I'm just an old-fashioned, humble hairdresser with a good eye."

He disputed the rumour Cameron needed help to conceal hair thinning on top.

"He's got plenty of hair, as much as he would care for, " Tahir said.

By shifting his parting, Cameron has joined other eminent "lefties" such as the Chancellor, Gordon Brown, President George Bush, and President Vladimir Putin. But former president Bill Clinton, former president Boris Yeltsin, and the most recent Tory prime minister, John Major, are all parted on the right. Tony Blair, typically, opts for the third way - a full head of hair but no parting.

Of course, previous Tory leaders William Hague and Iain Duncan Smith did not have to face such dilemmas. They are both bald.