HALIFAX -- Nova Scotia's Liberal government is accused of covering up an alleged impaired-driving incident involving a backbencher who resigned from the party caucus last weekend.

An email obtained by the opposition Progressive Conservative Party suggests the Liberals were aware last year of an incident involving Hugh MacKay that resulted in an impaired-driving charge earlier this month.

Premier Stephen McNeil has said he knew nothing of the incident until last week, but now it appears his chief of staff did know.

"I'd like to ask the premier: has the premier begun an investigation into how this email was handled?" PC leader Tim Houston asked in the legislature.

McNeil replied: "The reality is, the honourable member has tabled a document with all kinds of allegations with zero evidence."

The day after the provincial budget was tabled, it wasn't finances dominating question period.

"The question is, how long has the honourable member had the document?" McNeil said. "How long has he been sitting on it to use it as a political document?"

Houston replied: "I'll do something unique in this chamber, Mr. Speaker, I'll answer a question. Three hours. That's how long it took me to act when I saw that Mr. Speaker."

The firestorm surrounds MacKay, a former Liberal backbencher who is now sitting as an independent after being charged with impaired driving in relation to an incident in 2018.

The Progressive Conservatives released an email on Tuesday alleging the member for Chester-St. Margaret's was seriously impaired and driving before he crashed his vehicle in Tantallon, N.S., in November 2018.

Police say they got word of an incident almost exactly a year after and charges were laid earlier this month.

"On Feb. 12, 2020, Halifax District RCMP  served court documents on Hugh Wilson MacKay," said RCMP spokesperson Cpl. Lisa Croteau.

MacKay has kept a low-profile since resigning from the Liberal caucus on Sunday.

Last year, he pleaded guilty to a separate charge of impaired driving in October and released a statement acknowledging struggles with alcohol.

Wednesday, the premier said his chief of staff did get a call about the new allegations in May, but, after a number of inquiries, was told there was no substance to it, so the chain stopped there and the premier never learned of it.

While noting none of the allegations have been proven in court, McNeil says the unnamed author of the email should have gone to police first.

"If you have evidence of a crime, you take it to the police," McNeil said. "Don't bring it to a political party -- take it to the police."

The Tories say it's hard to believe McNeil never got wind of it before this week.

"If the premier didn't know about this, it speaks to a very, very dangerous culture within his party," Houston said.

The environment minister, a former caucus chair, says he'd never heard of problems with MacKay, but if he had, the premier would have been informed

At least one opposition leader appears to be siding with Liberals on the controversy.

"This is a matter that is best left to the deliberation of courts -- not to the floor of the legislature," said NDP leader Gary Burrill.

Houston said the fact that the police have laid charges is noteworthy.

"That was the evidence that was in the email that has merit," Houston said.

The matter dominated almost all of question period, and with the controversy far from settled, there will doubtless be many more inquiries in the days ahead.

As for the man at the centre of the story, he was not at the legislature on Wednesday. The Speaker's Office confirmed that MacKay has permission to be absent until at least the end of the week.

Through his lawyer, MacKay declined an interview request to CTV News.

MacKay has a court date on March 16 to deal with the new impaired-driving charge.