London: Stalking has become a specific criminal offence in Britain where some 120,000 victims, mostly women, are harassed annually.
The new law is expected to provide greater clarity around the offence for the police in England and Wales to improve the safety of victims and bring perpetrators to justice. In Scotland, stalking was made an offence in 2010.
The government has introduced two offences, stalking and stalking involving a fear of violence, the BBC reported.
The new law of stalking carries a maximum six-month sentence and stalking involving a fear of violence or serious distress carries a maximum five years in prison.
Campaigners had long claimed dealing with stalking under existing harassment laws was inadequate.
A parliamentary inquiry earlier this year found that about 120,000 victims, mostly women, were stalked every year.
However only 53,000 incidents are recorded as crimes by police - and only one in 50 of these reports leads to an offender being jailed.
The inquiry called for a new offence to be introduced at once, saying harassment and intimidation could often turn into murder.
After meeting victims and campaigners at Downing Street earlier this year, Prime Minister David Cameron had described stalking as "an abhorrent crime" which "makes life a living hell for the victims".
The calls for reform came after a series of cases involving stalkers who went on to kill, including Clifford Mills, 49, who stalked his ex-girlfriend Lorna Smith on Facebook before stabbing her to death at his flat in Brixton, south London, in February last year.
He was jailed in February for life, with a minimum term of 21 years, after being found guilty of murder.