The unions are concerned at the measures in the social-economic package agreed, including changes to pension entitlements and the possible scrapping of the annual indexation of pay. A one-day strike took place in December, and rail unions have also held protest actions of their own.

Marc Leemans, newly installed as general secretary of the ACV, recognised that there is little public support for the action. “I admit the unions are confronted with the pressure of public opinion,” he said last week. “We have a problem with explaining why we are striking.”

The rail unions have pledged they will strike from 22.00 on Sunday night. Although civil servants generally do not take part in strike actions, the lack of train services often causes a knock-on effect.

Among those definitely affected will be students of the Free University of Brussels (VUB), who have been told exams due on that day will go ahead as normal. A Facebook group has been organised to help students find accommodation in and transport to Brussels.

The main problem for the unions, Leemans said, is the lack of a government response to possible negotiations, despite promises made when the package of measures was first announced. “Di Rupo promised that we would be involved in the implementation of the socialeconomic measures, but there is no-one in the government working on that.”

Unizo, the organisation that represents the self-employed, said that the strike was “completely incomprehensible and irresponsible”. The unions are taking their action against the federal government, but at the expense of companies and anyone who wants to work, a statement said. “Our businesses are having to pay for government decisions over which they have no control,” said Unizo director-general Karel Van Eetvelt. “By bringing the country to a standstill, we are shooting ourselves in the foot in our attempt to fight the crisis.” An anti-strike petition organised by Unizo has gathered more than 61,000 signatures.

Federal minister for pensions Vincent Van Quickenborne, whose proposals to increase the retirement age are one of the main points of contention, said the strike was no longer necessary. “We have been negotiating intensely with the unions since 2 January,” he said. “There is the possibility for an agreement. Last week the private sector unions presented a list with their main problems, and we have agreed on solutions to 80% of those. The talks will go on; I want to solve this. But the unions need to realise they are playing with fire.”