Dave Wilson resigned as MLA for Glace Bay on Thursday. (CBC)

Nova Scotia Liberal Leader Stephen McNeil says he doesn't know why one of his caucus members suddenly resigned.

Dave Wilson, the Liberal MLA for Glace Bay and caucus chairman, informed McNeil late Thursday that he was resigning.

In an email to members of the news media on Friday morning, Wilson said he no longer feels he can fulfil his duties and responsibilities as an MLA.

"I would like to thank the people of Glace Bay for their support and for allowing me to serve as their representative for nearly 11 years," he wrote.

Wilson did not elaborate on why he is quitting politics and he did not return calls for comment.

Shortly after Wilson's resignation was announced, McNeil revealed that the province's auditor general — who is conducting an audit into possible irregularities in expense account spending — had requested a meeting with Wilson.

"On Wednesday, Feb. 24, Dave told me that he'd been contacted by the auditor general requesting a meeting on that Friday," McNeil said.

"On Feb. 27, Dave informed me that he had hired a lawyer and did not meet with the auditor general the previous day. He informed me that he had been instructed by his lawyer not to speak about the matter. I am not aware of the nature of the auditor general's questions."

McNeil said the next time he spoke with Wilson was when the MLA called to say he was resigning.

"I was certainly surprised at the phone call," he said.

McNeil said he did not know why Wilson was stepping down or why the auditor general wanted to speak with him.

Expense irregularities probed

Jacques Lapointe, Nova Scotia's auditor general, is investigating possible irregularities in expense account spending by more than one MLA.

When Lapointe released his original report on "excessive and unreasonable" claims by politicians in February, Wilson's expenses were highlighted for a $400 claim he made for patio furniture.

At the time, Wilson said that receipt was among several that were submitted and processed at once. He said it was a mistake and paid back the $400.

Last month, the two opposition parties in Nova Scotia released figures showing how much their members spent on extra staff and extra pay for their constituency assistants. The Liberals released the figures for six of the party's 11 members of the legislature.

Of those who submitted documentation, Wilson spent the most, confirming he paid his constituency assistant more than $24,000 on top of his regular salary over a year-and-a-half.

He also paid more than $37,000 over the course of three years to other staff.

Former staffers interviewed

Representatives from the auditor general's office were in Cape Breton on Friday speaking with former members of Wilson's staff.

One such staffer was Ann MacKenzie, who was Wilson's constituency assistant from 2002 to November 2008, when she was fired. MacKenzie is now involved in a dispute with Wilson over a wrongful dismissal complaint.

MacKenzie told CBC News on Friday that she received a few hundred dollars in a Christmas card as a bonus from Wilson on two different occasions. Other than that, MacKenzie said, she never received additional salary bonuses.

MacKenzie said she was asked by the auditor general's representatives not to comment on the contents of their meeting.

She said she felt as if "a huge weight has been lifted off my shoulders."

Wilson was first elected to the legislature in 1999 and has been re-elected five times. Before entering politics, the 54-year-old worked as a journalist in Cape Breton and Saint John, N.B.

With files from The Canadian Press