The singer and former X Factor judge Tulisa Contostavlos is to be charged with supplying class A drugs.

The Crown Prosecution service (CPS) authorised the Metropolitan police to charge the 25-year-old singer on Monday, who found fame with hip-hop group N-Dubz, following an investigation sparked by a newspaper sting.

"We have determined that there is sufficient evidence for a realistic prospect of conviction and that a prosecution is in the public interest," said Baljit Ubhey, London chief crown prosecutor at the CPS.

He said that police would charge Constostavlos with "being concerned in the supply of class A drugs".

Police launched an investigation following a sting by the Sun on Sunday, which alleged that Contostavlos helped arrange an £800 cocaine deal for an undercover reporter.

The newspaper ran the story following an investigation by the former News of the World undercover reporter Mazher Mahmood.

Contostavlos was allegedly filmed offering to supply cocaine through a friend at the Nobu restaurant in London. Her friend then allegedly sold half an ounce of cocaine at London's Dorchester hotel.

She will appear before Westminster magistrates court on 19 December.

"This charge relates to an investigation by the Sun newspaper between early March 2013 and 23 May 2013 which resulted in the supply of Class A drugs to an investigative journalist," confirmed Ubhey. "This decision to prosecute was taken in accordance with the code for crown prosecutors."

In August the singer's manager, Jonathan Shalit, said the Sun's story followed a deliberate attempt to entrap her. Her solicitor said she would plead not guilty.

The Sun has maintained that its investigation into the star was "entirely justified and in the public interest".

Contostavlos was arrested and bailed in June along with 35-year-old musician Mike GLC, real name Michael Coombs.

He has also been charged with allegedly supplying class A drugs and is due to appear at Westminster magistrates court on 19 December. Coombs has previously denied the allegation.

"This defendant is now the subject of criminal proceedings and has the right to a fair trial," said Ubhey.

The singer was officially dropped as a judge on The X Factor days before her arrest, with Sharon Osbourne making a return to Simon Cowell's ITV talent show in her place.

She rose to fame with N-Dubz but has failed to replicate that success as a solo artist, her debut solo album made it to only 35 in the charts.