OTTAWA • A top aide to Canadian Prime Minister Justin Trudeau resigned unexpectedly yesterday amid allegations that Mr Trudeau's office pressured the former justice minister to help construction firm SNC-Lavalin Group avoid criminal prosecution.

Mr Gerald Butts, Mr Trudeau's principal private secretary and a key architect of the Liberals' 2015 election victory, said in a statement he did not pressure then Justice Minister and Attorney-General Jody Wilson-Raybould over SNC-Lavalin.

Mr Trudeau, who faces a re-election bid in October, has faced criticism since Ms Wilson-Raybould quit his Cabinet following a Globe and Mail newspaper report this month that officials in his office had urged her to let SNC-Lavalin escape with a fine rather than face trial on charges of bribing Libyan officials.

SNC-Lavalin has said it had sought to avoid a corruption trial because the executives accused of wrongdoing had left the company and it had overhauled its ethics and compliance systems.

Any accusation that "I or the staff put pressure on the Attorney-General (Wilson-Raybould) is not true", Mr Butts said in the statement on Monday. He added that the allegation was distracting from the "vital work" Mr Trudeau was doing and that it was in the best interest of the Prime Minister's Office for him to step aside.

Mr Trudeau accepted Mr Butts' resignation and said he had served the country with "integrity, sage advice and devotion". "I want to thank him for his service and continued friendship," he said in a tweet.

Neither Mr Butts nor chief Trudeau spokesman Cameron Ahmad was immediately available for comment.

Mr Butts, 47, has known Mr Trudeau for more than 25 years, going back to when they were students at McGill University in Montreal.

Mr Butts was a polarising figure inside the Liberal Party, where some dubbed him PMGB - short for Prime Minister Gerald Butts - and complained privately that he had too much influence.

Ms Wilson-Raybould has not commented on the matter, citing solicitor-client privilege. But Mr Butts' resignation fuelled an opposition demand to drop the privilege.

"It is now more important than ever before that Mr Trudeau waive solicitor-client privilege so Jody Wilson-Raybould can tell her side of the story to Canadians," Conservative leader Andrew Scheer said in a statement.

Ms Wilson-Raybould was shuffled to Veteran Affairs in January, a move widely seen as a demotion for one of Canada's most prominent indigenous federal politicians.

REUTERS