Michael Dalton, a former police informer, and his partner, Nikki Chen, trafficked women from China to work in the brothels. They spent the profits on houses in Gloucestershire and Surrey, two Ferraris, a Lamborghini and classic Mercedes cars.
Police believe that a VW van, fitted with a cage, was used to ferry the girls between the brothels.
Dalton, 44, of Leatherhead, was convicted of conspiracy to traffick people for sexual exploitation after a trial at Croydon crown court.
Chen, 56, admitted trafficking for sexual exploitation at an earlier hearing. The pair were arrested after a nine-month surveillance operation by Scotland Yard’s vice squad.
Undercover police observed at least a dozen customers visiting each of the brothels every day. Girls worked in terrace homes in Sunbury, Egham, West Drayton and Surbiton, charging between £60 and £120.
One officer told the court that Dalton shouted “customer” to girls in one brothel, when he entered the address. Dalton claimed he was a police informant who had been trying to free trafficked prostitutes.
The women were forced to work to pay off debts they owed the couple and told their families they would be at risk if they tried to run away. Police believe at least £1 million a year went through the couple’s bank accounts.
One detective said: “This was a major criminal enterprise which was running beneath the radar and involved some of the worst exploitation of women we have come across.”
The court heard that police had stopped using Dalton as an informant years ago and warned he would be prosecuted if he committed a crime.
Chen and Dalton were also convicted of money laundering offences and control of prostitution for gain.
Chen has surrendered £250,000 and Dalton is also expected to be ordered to repay money. Two other men, Manjit Singh, 33, of Maidenhead, and Ian Garrett, 43, of Epsom, admitted conspiracy to traffick people. All four will be sentenced next month.
Police rescued seven women when they raided the brothels.
Detective Chief Superintendent Richard Martin, head of the Met’s Human Exploitation and Organised Crime Command, said: “Chen, Dalton and their co-conspirators had a blatant disregard for the women they had brought into, and moved around the UK, with the promise of a better life.
“The young women they controlled were exploited and obliged to have sex with more than 12 strangers a day, in order to pay off the debts they had accrued in being trafficked to the UK on false passports and visas.
“Any woman who is being violated by people like Chen and Dalton should not be afraid to come forward.”