London: Upskirting, which involves offenders taking a picture under a person's clothing without their knowledge, has now become a criminal offence in the UK after an 18-month campaign. Perpetrators of such a crime face up to two years in prison and being placed on the country's sex offenders register after the Voyeurism Bill received Royal Assent from Queen Elizabeth II to become law on Tuesday.

"As the Queen formally agrees to make our bill into an Act of Parliament, we should see this campaign as not only essential legislative change, but also proof that normal people and grassroots campaigning can make a real difference," said Gina Martin, a victim of upskirting, who led an 18-month campaign to ensure it is recognised as a criminal offence.

"It has been a long time coming but we are finally protected in every scenario as we should always have been," she said.

The new law will come into formal effect from April, two months from Royal Assent being granted.

The UK government said the new law will ban the degrading practice to deter perpetrators, better protect victims, and bring more offenders to justice.

"Those who commit such a degrading act will face prison, and victims' complaints will be dealt with seriously," said UK Justice Minister Lucy Frazer.

"Gina Martin and other victims, charities and MPs supporting her should be immensely proud. Her efforts show how one campaigner can work with government to change the law for everyone," she said.

Martin began her campaign after two men took a picture up her skirt at a festival. The UK government intervened in June last year to bring forward measures to tackle this behaviour, after a Private Members Bill did not pass its second reading. The government-backed legislation has since successfully passed through both Houses of Parliament.

Until this new law was passed, the behaviour was prosecuted under the offence of Outraging Public Decency. However, following concerns raised by victims that not all instances of "upskirting" were covered by current law, the government acted to create a new, specific offence.

The Voyeurism Bill outlaws 'upskirting' where the purpose is to obtain sexual gratification, or to cause humiliation, distress or alarm. This includes instances where culprits say images were just taken "for a laugh" or when paparazzi are caught taking intrusive images.

It creates two new offences under the UK's Sexual Offences Act 2003 to capture this behaviour. The British Transport Police has reported a 178 per cent rise in the number of 'upskirting' incidents from 2013-2017.