The number of illegal workers in the building trade has almost halved to 18 percent last year, the Labour Inspectorate reports. In 2007 checks revealed that 30 percent of employees in the Dutch building sector lacked the required work permits.

The downward trend has been evident for years, but the Inspectorate says the 2008 figures are "spectacular".

The Labour Inspectorate says the reduction is due to increased checks and higher fines. A further reason is that many East-Europeans, such as Poles and Czechs, no longer need a work permit for the Netherlands.

Most illegal workers in 2008 were Bulgarians and Romanians. Many employers, according to the Inspectorate, are attempting to bend the rules by formally hiring Bulgarians and Romanians as subcontractors, while their work relationship remains no different to that of employees. If they are found out, employers will be fined, the Inspectorate says.