Police Scotland said on Wednesday that a 58-year-old man had been arrested as part of an investigation into Scottish National Party funding and the BBC reported the man was the husband of the former Scotland leader Nicola Sturgeon.
Peter Murrell, 58, who stood down as the chief executive of the governing pro-independence party last month, was taken into police custody on Wednesday morning, the BBC said.
The police investigation is looking at what happened to more than 600,000 pounds ($748,920) raised by Scottish independence campaigners in 2017, which was supposed to have been ring-fenced for spending on that issue but was missing from party's filed accounts.
The SNP did not immediately respond to a request for comment. The Scottish government said it was a matter for the party.
Murrell, who had run the SNP for more than two decades, resigned last month after accepting blame for misleading the public about a plunge in the number of party members.
His wife Sturgeon also stood down as the leader of Scotland's semi-autonomous government last month after eight years in power, saying she had become too divisive to lead the nation to independence.
Scotland voted against independence by 55% to 45% in 2014. Britain's vote to leave the European Union two years later when a majority of Scots wanted to stay, and Scotland's handling of the coronavirus pandemic brought new support for independence.
Police Scotland said they were carrying out searches at a number of addresses as part of the investigation.
"The man is in custody and is being questioned by Police Scotland detectives," the force added.
