Arthur Wagner, a member of the far-right Alternative for Germany (AfD) party who is known for its anti-Muslim rhetoric, has surprised observers by converting to Islam.
He sat on the party's executive committee in the state of Brandenburg but recently stepped down for reasons he says are unrelated.
The 48-year-old, who is still a member of the party, told one newspaper that it was a "private matter".
On its website, the AfD proclaims that "Islam does not belong in Germany".
AfD supporters have regularly held anti-Islam rallies, and in last year's federal elections the party used posters depicting housewives in niqab (face veils) to press home its message, says a BBC report.
But a spokesman for the party in Brandenburg has insisted that Wagner's conversion is "no problem" for the party.
"Religion is a private matter. We support the constitutional right of religious freedom," Daniel Friese was quoted as saying.
Wagner, who is of Russian origin, previously belonged to German chancellor Angela Merkel's Christian Democratic Union (CDU) party.
However in a video published in 2017, he is shown saying that although he had once been an admirer of Merkel, her decision to open the door to hundreds of thousands of migrants during the 2015-16 crisis had proved he was "totally wrong".
He claimed Germany had "mutated into another country" as a result.
Wagner was also listed as previously belonging to a group called "Christians in the AfD".
The AfD won its first parliamentary seats in the last election, becoming the third party with 12.6% of the vote.
