Liberal MLA Michael Murphy announced on Monday that he was resigning as justice minister and will quit provincial politics in five weeks. (CBC)

Former Justice Minister Michael Murphy's sudden departure from provincial politics could open the Liberal government up to attacks that the party is cracking under pressure from the proposed NB Power deal, according to a political scientist.

Murphy announced on Monday that he was leaving the cabinet and in five weeks he would retire as the MLA for Moncton North, about seven months before the Sept. 27 election.

Tom Bateman, a political scientist at St. Thomas University, said Murphy's explanation that he wanted more time to spend with his family is often used by politicians who don't want to admit the real reason they are stepping down.

'Certainly the deal's critics are going to suggest that Mike Murphy has had his doubts and cannot or will not support the deal going into the next election.'— Tom Bateman, St. Thomas University political scientist

Bateman said critics of the NB Power deal are already drawing conclusions of their own of why Murphy is really stepping away from political life.

"Certainly the deal's critics are going to suggest that Mike Murphy has had his doubts and cannot or will not support the deal going into the next election," he said.

Murphy told reporters at a news conference outside his constituency office that he supports his government and said that changes to the deal to sell NB Power to Hydro-Québec are on the way.

At the same news conference, Murphy failed to answer a question about whether he would ever consider a return to politics. Instead, he talked about his desire to immediately return to practising law.

Murphy tested the political waters in 2001 about a potential run for the Liberal leadership after former premier Camille Theriault resigned. However, he backed away from a leadership challenge, saying he wanted to spend more time with his family, practise law and finish his master's degree at Osgoode Hall Law School in Toronto.

Premier must show solidarity

Bateman said the premier has to make sure all of his remaining MLAs are on board with the deal and then he has to live up to Murphy's promise.

"The premier has to perform on that to make sure that what we have right now will be improved," Bateman said.

"I think that's the message of Mike Murphy's carefully chosen words not to express support for the MOU as it is but to support the government's position and to signal there's more to come from the premier's office."

Bateman did offer the Graham government some reason for optimism. The political scientist said the opposition to the power deal has been so strong that opinion of the Liberal government doesn't have anywhere to go but up.

Murphy's decision to resign as a MLA in five weeks means that he will not be in the legislative assembly to vote on the contentious NB Power deal in March.

Under the Elections Act, the premier must call a byelection within six months of a vacancy being declared.

Murphy's decision to wait to resign his seat until February means the byelection would occur in mid-August at the latest. However, New Brunswick's fixed election date is Sept. 27, so if the general election was called during the byelection then the Moncton North vote would be rolled into the provincial campaign.

There are 33 Liberals and 22 Progressive Conservatives in the 55-seat legislative assembly