More than 150 properties in the Fens were visited in the first three months of this year, during a crackdown on rogue landlords and gangmasters.

Operation Pheasant brings together police, fire officers, Fenland Council, the Gangmasters Licensing Authority, HM Revenue and Customs, and immigration officers.

Inspections of 158 properties were carried out between January and March this year, bringing the total number to 478 since the operation was launched in 2012.

Hundreds of benefits offences and six cases of human trafficking have been uncovered and 20 people voluntarily repatriated.

Some 166 cases of exploitation by illegal gangmasters have also been uncovered and 44 people found alternative accommodation after being found to be illegally housed. Landlords have been ordered to fix hazards such as faulty electrics.

Fenland Council cabinet member Will Sutton said: 'Conditions in too many rented properties remain poor and overcrowding is still a major issue.

'Our priorities are to make sure all landlords comply with housing legislation, maintain decent living conditions and prevent the widespread exploitation and harassment that has gone on.

'There is a real need for more private rental homes that are of decent quality, safe and properly managed and are affordable to people on comparatively low incomes.'

Chief Insp Robin Sissons said: 'Operation Pheasant has uncovered some serious crimes that we previously didn't know were happening.

'It is important that we act because this is about vulnerable people that are being subjected to exploitation due to the greed of others. That has got to be wrong in anyone's book.'