Faculty of Public Health president said lowering age to 15 could 'draw a line in the sand' against sex at 14 or younger

Downing Street and Nick Clegg have joined forces to reject a call by a leading public health official to consider lowering the age of consent to 15.

A spokesman for the prime minister said the current age of 16 was designed to protect children, a view echoed by the deputy prime minister who rejected a "blanket reduction" in the age of consent.

Professor John Ashton, president of the Faculty of Public Health, had called for a lowering of the age of consent to make it easier for 15-year-olds to seek contraception and sexual health advice from the NHS. Figures show that up to a third of teenagers have sex before they reach 16.

Ashton told the Sunday Times: "Because we are so confused about this and we have kept the age of consent at 16, the 15-year-olds don't have clear routes to getting some support. My own view is there is an argument for reducing it to 15 but you cannot do it without the public supporting the idea and we need to get a sense of public opinion about this.

"I would not personally argue for 14 but I think we should seriously be looking at 15 so that we can draw a line in the sand and really, as a society, actively discourage sexual involvement under 15. By doing that, you would be able legitimately to organise services to meet the need."

Downing Street gave the proposal short shrift. A spokesman told the BBC: "We reject the call to lower the age of consent. Current age is in place to protect children and there are no plans to change it."

The deputy prime minister echoed No 10. Asked on the Andrew Marr Show on BBC1 what he thought of Ashton's call, Clegg said: "I am not in favour of that. The age of consent has been a British law for generations in order to protect children.

"This health expert is right in saying there is a problem – we have far too high levels of teenage pregnancy. I am worried, like everybody is worried, about the sexualisation, the culture and the information so many young people are bombarded with. That is why I am constantly urging Michael Gove to update and modernise sex education in schools, which has not kept up with the internet age.

"But do I think simply a blanket reduction in the age of consent is the answer to this difficult dilemma? No. So yes there is a problem. Yes we need to a debate. Yes we need to update sex education. But this is not the answer."

The deputy prime minister also said he was formally pressing Cameron and George Osborne to raise the threshold for the personal tax allowance to £10,500 by the time of the next general election.

The Tories are expected to agree to the "worker's bonus", which would exempt an extra 500,000 people from paying income tax. It is one of the Liberal Democrats' signature policies. The Lib Dems say they have been the main driving force behind raising the personal tax allowance from £6,475 since 2010.

Clegg said Lib Dem support for raising the personal allowance showed why his party was rooted in the centre ground, unlike the Tories and Labour. He said: "On long-term fiscal policy it is too important for our country to have parties lurching to the right or the left.

"You appear to have this view from the right now that taxes should never go up and you should be shrinking the state to an ever smaller size in a slightly ideological way. In the same way the left are making a mistake in thinking you can repeat all the mistakes of the past and borrow and spend more and more and more and bloating the state. I don't think we should be ideological about this."