Members of political parties GroenLinks and the PvdA have voted to include the abolition of the monarchy in their joint manifesto for the November general election.
Some 52% of delegates to the joint party conference in Rotterdam on Saturday voted in favour of the motion to establish a parliamentary republic, with 42% against.
The motion’s backers say that a monarchy and a line of succession is a leftover from the past, is part of a system of inequality and expensive. The Dutch royal house has a budget of some €55 million next year, making it one of the most expensive monarchies in Europe.
The joint manifesto currently includes a commitment to restrict the monarch to ceremonial roles only and to ensure they pay tax, but this vote goes further than that.
Nevertheless, the likelihood of the monarchy in the Netherlands ever being abolished is still a very long way off and would require a two-thirds majority in parliament.
Support for the monarchy has been declining in the Netherlands in recent years. A survey into the popularity of the royal family last month showed the king merits a score of 6.6 points out of 10 while queen Maxima scores 7.1, down slightly on a year ago.
Some 50% of the general population support the monarchy but 26% would like the Netherlands to become a republic.
Among the under 35s, almost four in 10 support the monarchy but 34% consider themselves republicans.