Thirteen children were among 167 victims of human trafficking recovered by police, the Home Office said on Wednesday, in a six-month crackdown which led to 528 arrests.

The investigation involved 55 police forces who searched over 800 premises including residential apartments, massage parlours and nail bars and rescued 167 women forced into prostitution or servitude.

The victims were mostly from China, southeast Asia and eastern Europe.

"We still have an insidious problem in the heart of our society," Dr Tim Brain, of the Association of Chief Police Officers told reporters.

Brain added that of those arrested, 88 had been charged with offences including the trafficking of humans, brothel management and money laundering.

"We have some way to go before human trafficking investigation is core business for every single police force," Brain said.

Many of the premises investigated were in "ordinary" suburban areas, Brain said, used as fronts for brothels with neighbours largely unaware of illegal activity taking place.

Home Office Minister Vernon Coaker said one of the main problems facing police was encouraging victims to speak out against traffickers and accept help from the police and non-governmental organisations (NGOs).

"Our biggest challenge is to work with NGOs to really get to grips with how we can encourage victims to come forward and work with us," Coaker said, adding that many victims, particularly children, resist help and refuse to speak out.

"It has to be said that although we had support and protection measures in place . the actual number of victims that accepted support is low," Coaker told reporters at a briefing.

The investigation, named Operation Pentameter 2, also found that children born in, or residents of, Britain were also being "internally trafficked" for purposes of sexual exploitation.