Adults befriending children with the intention of abusing them face five years in jail as part of the first radical overhaul of sex laws for 50 years.

The new offence of sexual "grooming" of children will allow police officers to intervene and arrest a suspect before any sexual activity takes place.

New sex offences and maximum jail penalties

Rape of a child under 13 - life Sexual activity in public - six months Meeting a child following sexual grooming - five years Sexual activity with a person with a mental disorder - Life Paying for sex with a child - 14 years

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But Home Office minister Hilary Benn said that while he did not "under-estimate the difficulties" of bringing such a prosecution, it was the government's view a new offence was needed to protect children.

Among other measures in the Sex Offences Bill published on Wednesday, couples who have sex in an outdoor public place could face six months imprisonment

Sex offenders from overseas will now have to register when they come to the UK.

Chatrooms

UK sex offenders will have to re-register annually, instead of every five years, or face five years in jail.

Home Secretary David Blunkett said sexual crime, especially against children "can tear apart the very fabric of society".

"Protection of children and the most vulnerable is a priority for the government," he said.

Blunkett says current laws are archaic

"This is now the first time for 50 years a government has had the courage to take on the difficult and sensitive task of reforming sex offences legislation."

The new offence of "sexual grooming" comes in two parts, dealing with the intention of a would-be paedophile and the moment a meeting with a child takes place.

Mr Benn told journalists that if it became known that a 45 year old man was logging on to Internet chatrooms pretending to be a 15-year-old, then a civil preventative order could be made.

Gap in the law

"That's the first protection, to try to catch this behaviour and stop it before a meeting and any risk of any sexual activity with the child takes place," he said.

"Secondly there's the grooming offence ... committed at the moment the meeting takes place - you have to prove that they intended to commit a sexual offence with that child ..."

But Mr Benn stressed: "I don't underestimate the difficulties that there may be involved."

Penny Dean, of the Children's Society, welcomed the stance taken on child abusers.

Sarah Payne's case added to fears on paedophiles

But John Wadham, director of civil rights group Liberty, said: "Provisions like those on grooming risk feeding fear and mistrust in ways that distract from the serious business of child protection - which is about openness, education and talking frankly with our children."

Harry Fletcher, of probation union Napo, said the police may have difficulty proving cases under the grooming law.

Under the new laws, anyone found guilty of having sex with a child aged 12 or under would be charged with rape, with a maximum penalty of life in prison.

This would stop defence counsel from asking youngsters "did you lead him on".

Sex outdoors

Inducing a child to take their clothes off will carry a maximum 10-year sentence if no physical contact was involved, and 14 if there was.

The measures also include a six month jail term for a person who "knows or is reckless" about whether they will be seen having sex.

Private homes are exempt from the new law, but having sex in a private garden which can be seen from the street would be a crime.

Sex in public toilets, or "cottaging", will not be a specific offence unless "the cubicle door was open", said Mr Benn.

Rape convictions

The bill introduces a new test of "reasonableness" over the issue of consent in rape allegations.

This would mean rape victims would be considered to have been unlikely to have said yes to sex if they were unconscious or threatened, for example.

"Date rape" will not become a separate offence, but using drugs or other substances to stupefy a victim for an indecent assault will carry a 10-year sentence.

It is hoped conviction rates for rape - which fell from 25% in 1985 to just 7% in 2000 - will improve.

The bill includes new offences covering sexual assault by penetration, bestiality, voyeurism, indecent exposure, and sexual interference with human remains.

New measures against child prostitution are also included.