OTTAWA — Weeks after settling a $5-million defamation suit, NDP MP Pat Martin has let the mouth that keeps on giving roar again with another profanity-laced attack on Conservatives.

The Manitoba backbencher with a reputation for epic, foul-thumbed Twitter tirades erupted again Thursday, calling the Conservatives "dirty, rotten bastards" in an interview with Hill news website iPolitics.

Martin's verbal rant was prompted by a direct-mail campaign by Tories into his Winnipeg Centre riding, promoting the government's handling of the economy, job creation and tax cuts while taking shots at NDP policies.

The mailing, signed by 10 Manitoba Tory MPs, also included a survey seeking input on which party is best qualified to govern among other data.

In the interview, Martin accused "institutionally sociopathic" Conservatives of abusing tax dollars by using House mailing privileges to target him.

He complained MPs aren't permitted to bombard ridings other than their own with mass mailings — something parties routinely do.

Conservatives said Martin's erratic behaviour and outbursts are hurting him in his riding and say no rules were broken by contacting his constituents.

Manitoba Tory caucus chairman Robert Sopuck questioned Martin's understanding of the rules.

"The NDP is the party that invented political hardball," said Sopuck.

"They are ruthless and relentless. And I guess they don't like it when other parties are vigorous as well."

The black sheep of the New Democratic caucus was pressured to delete his Twitter account in December after he called Conservatives "rat-faced whores."

Mark.Dunn@sunmedia.ca

Twitter:MarkDunnSun