The tax office will press ahead with extra checks on sham self-employment from January 1, despite calls for a delay, department officials told MPs at a hearing on Thursday.

Legislation which determines who is “really” self-employed from those who have one employer and should be on contract was introduced eight years ago but has never been fully enforced. But that is set now to change.

“Further delays would mean losing momentum,” civil servant Berry Roks told the hearing. In addition, it would disadvantage companies and people who are sticking to the rules, Roks said.

The initial checks will focus on companies rather than the self-employed themselves and bosses will first be given an official warning, rather than a fine.

Organisations representing the self-employed have said that their members are already losing contracts because their employers are worried that they are not meeting the new regulations.

Earlier this week, the security sector warned that there could be problems recruiting enough security guards for big events and the VVD has also called for a “soft landing”. The tax office should focus first on sectors where people are forced to work as freelancers or zzp’ers against their will, the coalition party said.

The new legislation states that someone is really self-employed if they carry financial risks, have their own tools and other equipment, have specific expertise that the company renting them does not have and present themselves as a freelancer while working.

Contracts should also be short, and the freelancer have multiple clients, make investments and be responsible for their own admin.

Freelancers are cheaper for employers because they do not have to pay income tax and social insurance premiums on their behalf, and they are not entitled to holiday or sick pay.

This, the unions argue, has led to a surge in sham self-employment as employer try to get out of their responsibilities and is putting undue pressure on people who are in permanent jobs.

The Netherlands has some 1.7 million registered self-employed, according to Chamber of Commerce figures. According to national statistics agency CBS, some 13% of the working primarily earn most or all of their income as a freelancer.