A man who became a police informant while working in a Surbiton brothel was duped by his girlfriend about the fact she was using trafficked Thai prostitutes, he claimed in court this week.

Michael Dalton, 43, said he was tipping off both Surrey Police and the Metropolitan Police about the brothels in the run-up to his arrest, and had been acting as a police informant.

Prosecutors at Croydon Crown Court said he was using his past as an informant to escape conviction for his involvement in four brothels and said police had deregistered him as an informant before he was arrested in raids in July 2009.

He told the jury his co-defendant and Taiwanese girlfriend Nikki Chen, 55, who lived with him in Leatherhead and with whom he had an “up-and-down” relationship, duped him about her involvement in sex trafficking, when he tried to persuade her to stop.

But he admitted he had “no moral values” or objections to women working in brothels.

Chen pleaded guilty at the start of the trial to running four brothels and conspiracy to traffic women into the UK for sexual exploitation.

On Tuesday, Mr Dalton said: “As I became more aware of the situation and how these girls came into the country and the way they had to work off these debts I wasn’t happy with the situation at all and I wasn’t happy with her being involved in it.

“I had no real moral values on women who want to work as prostitutes. If they do it off their own backs, it is up to them but these girls were being pressured and forced into these situations and were having to pay a huge debt before they could make their own money themselves and I didn’t agree with that.”

Asked if he tried to talk to Chen about his concerns, he said: “I did but it fell on deaf ears to be honest.

“If there’s a word duped, I was duped by her. She would say I’m going to stop working with illegal girls so I don’t get in trouble with the police.”

Questioned on how he came to speak to the prostitutes, he said: “Just really going along to the premises, speaking to them. Just generally chit-chat. If I spoke to them on their own they were more willing to speak to me.”

He also denied police suggestions he had become obsessed with one of the Thai prostitutes, a woman known as Ploy, and had an ulterior, sexual motive for trying to help her and other women out of debt bondage.

He said: “I became quite close to her. It wasn’t a sexual relationship. It was a close relationship. If it had turned into a sexual relationship I would have become just another customer and she wouldn’t have provided me with information.”

Earlier in the day, Mr Dalton told the court his healthy finances – the pair had two Ferraris and property in Gloucester and Leatherhead – were down to his work in the building trade and remortgaging properties.

The jury also heard about his previous convictions - a fine for stealing a TV and video from a school in 1987, a conviction for driving while disqualified for speeding offences, and a community penalty and compensation to his victim for a common assault after a road rage incident in 2001.

The trial continues.