LONDON (Reuters) - A police officer was forced to resign on Wednesday for having sex with a prostitute at a building he had been sent to investigate to see if it was a brothel.

The police sergeant, who was not named, had "engaged in sexual activity with a sex worker" while on duty in east London in December 2005, the Independent Police Complaints Commission (IPCC) said. He was supposed to be finding out if the premises were being used for prostitution.

"The sergeant's behaviour was disgraceful. He has brought shame on himself and his former colleagues," said IPCC Commissioner Deborah Glass.

The sergeant, who had faced four disciplinary charges, was forced to quit after a misconduct hearing.