The RSZ, together with the social information and investigation service SIOD, is currently working on 4,679 fraud cases in all sectors, more  than one in ten of the 43,000 files it dealt with in 2010.

Because construction is known to be a sector vulnerable to social fraud, contractors  are obliged to declare a site in advance to allow checks. But many still don’t, the RSZ reports.

In June, the government agreed to bring in a  system under which everyone present on a site wears a unique identification badge issued in advance. Whenever a worker is not required  or cannot work, his absence from the site is registered to prevent working off the books.

Social inspectors will also have access to a new  computer system containing social security and tax data. The intention is to push the proportion of fraud cases brought to light from 25% at  present to a target of 65%.