Britain's three main political parties 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 Nick Clegg, the deputy prime minister, who rejected a "blanket reduction" in the age of consent.
Labour said the move would not tackle teenage pregnancy.
The three parties were responding after Professor John Ashton, president of the Faculty of Public Health, 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. Up to a third of teenagers are thought to 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 to legitimately organise services to meet the need."
Downing Street gave the proposal short shrift. A spokesman said: "We reject the call to lower the age of consent. The current age is in place to protect children and there are no plans to change it."
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 a debate. Yes, we need to update sex education. But this is not the answer."
The Department for Education dismissed Clegg's call for a change to the guidelines on sex education. A spokesperson told the BBC that existing guidance provided a sound framework for sex and relationship education.
Luciana Berger, the shadow public health minister, endorsed Clegg's call for sex education to be updated as she also rejected the call to lower the age of consent. "Lowering the age of consent is not the way to tackle teenage pregnancy and we are against such a move. The teenage pregnancy rate fell substantially under the last Labour government. But sexual health clinics are now closing their doors and young people are struggling to get appointments.
"Labour has called for improved sex and relationship education and tabled amendments to recent legislation for it to be made mandatory, not voluntary, in all schools. Regrettably, the change was voted down by Tory MPs."
