David Cameron has urged police to carry out a "thorough" probe into a company running the Government's flagship scheme to cut unemployment.

Officers have arrested four former staff from A4e, whose chief executive Emma Harrison has advised Mr Cameron and which operates the coalition's Work Programme to help the jobless find employment.

Labour MP Fiona Mactaggart said since May 2010 A4e had won contracts from the Department for Work and Pensions worth £224 million.

She added: "In view of the fact there are record numbers of unemployed people and that employees from this company have been arrested, what action are you taking to make sure neither vulnerable unemployed people nor the taxpayer are victims of fraud by A4e?"

Speaking at Prime Minister's Questions, Mr Cameron said: "The investigation needs to be thorough, it needs to get to the truth and then we can take into account its findings."

He told the Commons the allegations went back to a scheme run under the previous Labour government, adding: "As I understand it was the company itself that raised the issue with the relevant authorities."