An 18-year-old Briton who had a sexual relationship with a 17-year-old British girl in Dubai while the pair were on holiday with their families has been sentenced to one year in prison, a campaign group has said.

Marcus Fakana, of Tottenham, north London, began the secretive holiday romance in September with another Londoner, who is now aged 18.

After returning home and seeing pictures and chats, the girl’s mother reported the relationship to Dubai police, who then arrested Fakana at his hotel. Sex with another person aged under 18 is illegal in Dubai.

Detained in Dubai called the judgement an “utter disgrace” and said Fakana would appeal the “unreasonable” sentence.

The organisation, which helps foreigners abroad and is an international authority on UAE law, added that Fakana felt “abandoned by the British government”.

A UK Foreign, Commonwealth and Development Office spokesperson said: “We are supporting a British man in the UAE and are in contact with his family.”

The Dubai Public Prosecutor’s office has been approached for comment.

Radha Stirling, the founder and chief executive of Detained in Dubai, said Fakana, who has been unable to leave the country since September, was “desperately hoping” to return home this week.

“But prosecutorial mishandling in the first stages of the case meant it wasn’t heard as a misdemeanour when it should have been,” she said.

“The family have issued a plea to Dubai ruler, HH Sheikh Mohammed Al Maktoum, to spare Marcus for consensual sex with another British citizen.”

Ms Stirling added that the teenager would be deported following his sentence.

She previously said that his parents “don’t know what to do” and had to return to London without their son to resume work as a cleaner and in a warehouse.