Tax minister Folkert Idsinga has resigned after coming under increasing pressure to reveal the scope of his €6 million investment portfolio.

Idsinga, a minister on behalf of “good governance” party NSC will give a statement on the reason for his resignation later on Friday. He is the first member of the cabinet to resign since ministers were sworn in in July.

Earlier this week a majority of MPs had backed calls for full disclosure. Idsinga, a former VVD MP who joined Pieter Omtzigt’s NSC party last year, declined to reveal which companies he held shares and other financial interests in, claiming it was a “private matter”.

On Tuesday Geert Wilders, whose far right PVV party is the largest in the coalition, added his voice to those demanding a breakdown of the minister’s financial affairs.

“This doesn’t look like good governance or a solid justification to me,” Wilders posted on social media site X.

Wilders’ words were a direct reference to NSC’s election campaign pledge to create a more robust, transparent system of government where MPs are more accountable to parliament.

His comments are also a further sign of the tension between the four coalition parties, with the NSC and PVV at odds over tackling immigration in particular.

Idsinga said earlier this week he had discussed his interests during the formation of the cabinet and put his businesses “at arms’ length” when he accepted the post of minister for tax affairs.

But opposition parties including GroenLinks-PvdA, D66 and the Socialist Party (SP) said Idsinga should release the full details of his financial holdings to ensure there was no conflict of interest.

Idsinga told RTL Nieuws, who published the original story based on the annual report of his financial holding company, that he supported transparency in government.

“But there is such a thing as people’s private lives,” he said. “I do my best to be as transparent as possible within the rules as stated and I don’t see why I should go any further than that.”