CALGARY - Opposition parties clamoured Thursday for the Conservatives to turf a Calgary candidate for making intolerant remarks about immigrants.

But Lee Richardson, the incumbent MP seeking re-election in Calgary Centre, brushed off calls that he step down for suggesting that immigrants are prone to commit crimes.

Richardson's comments threaten to undo a vigorous Conservative effort led by Jason Kenney -- the party's liaison to minority groups and the Tory candidate in the adjacent riding of Calgary Southeast -- to woo immigrant voters.

"Look at who's committing these crimes ... They're not the kid that grew up next door," Richardson told the Calgary newsmagazine Fast Forward Weekly.

"Particularly in big cities, we've got people that have grown up in a different culture," he said.

"And they don't have the same background in terms of the stable communities we had 20, 30 years ago in our cities and don't have the same respect for authority or people's person or property."

Richardson later said he regretted the remarks and was referring to a "small minority" of people.

"I soon realized that my comments could be misconstrued in a way that does not reflect my longstanding support for immigration and diversity," he said in a statement released Thursday.

"That's why even before the article went to print I clarified my intent, and expressed regret for the words that I chose.

"I stand by my retraction. Those who have known me through my long time in public service know that I have always supported immigration, have worked closely with our cultural communities, and have regarded diversity as one of our greatest strengths."

But the opposition demanded his head.

"This is awful. He should be fired right away. There is no hesitation possible," said Liberal Leader Stephane Dion, raising the spectre of the Alberta-based right-wing Reform party, which merged with the Tories in 2003.

"It's the roots of what was wrong in the Reform party. Not all Reform supporters were like this, but it was what was wrong in this party. This kind of intolerance, we cannot tolerate that."

Added Liberal Ujjal Dosanjh: "If Prime Minister (Stephen) Harper does not take action and fire his candidate, one can only assume he condones such attitudes.

"It's clear that the old Reform party view toward immigration is still alive and well in this Conservative party."

As far as the Conservatives are concerned, it's case closed, said Kory Teneycke, a spokesman for Prime Minister Stephen Harper.

"Mr. Richardson has clarified his remarks," Teneycke told reporters travelling with the prime minister. "From our perspective, the matter is over."

Heesung Kim, the Liberal candidate in Richardson's riding and herself an immigrant from South Korea, denounced Richardson's comments as "disturbing."

"To say that if you weren't born and bred in Canada then you're more likely to be a criminal is completely unbelievable," she said.

Richardson wasn't the only candidate in hot water Thursday.

The Liberals were also urging NDP Leader Jack Layton to fire his candidate in the Ontario riding of Durham, east of Toronto, for inappropriate comments on the Internet.

In Facebook postings about U.S. war deserters during the summer, Andrew McKeever used vitriol and obscenities to refer to a woman, and also threatened to beat up a critic.

"I took part in several online discussions over the last few months and was often a less than respectful contributor, exchanging insults with other members," McKeever said in a statement late Thursday.

"I am deeply sorry for having offended anyone."

Past comments also haunted Lesley Hughes, the Liberal candidate in the Winnipeg riding of Kildonan-St. Paul, who issued a statement late Thursday defending herself against allegations of anti-Semitism.

Internet bloggers have been hashing over an old column in which Hughes, a freelance journalist, suggested that Israeli intelligence warned the United States in advance of the 9-11 attack on the World Trade Centre and "Israeli businesses" vacated the premises before the attack.

Hughes also referred readers to websites asserting "CIA foreknowledge and complicity of highly placed officials in the U.S. administration around the attacks on the twin towers."

In her statement Thursday, Hughes described herself as a "lifelong friend and supporter of the Jewish community in Winnipeg" and said she finds it "personally offensive" to be accused of anti-Semitism.

Nevertheless, she said, "I heartily apologize for that perception."

The controversy surfaced a day after Dion made a campaign stop in Winnipeg to promise millions in federal cash for security at churches, mosques and synagogues targeted by bigots.

The Tory war room countered the Grit offensive against Richardson by noting Liberal candidates Hedy Fry, Garth Turner and Keith Martin have also made inappropriate remarks linking immigrants and crime.

But the war-room spinners didn't mention that their respective remarks were made when Turner was a Progressive Conservative MP and Martin a Reformer.

Richardson was first elected as an MP under the Progressive Conservative banner in 1988. He lost his seat in the 1993 campaign but was re-elected as a Conservative in 2004 and 2006.

He also served as chief of staff to former Alberta premier Peter Lougheed and deputy chief of staff to former prime minister Brian Mulroney.

Richardson didn't return messages left Thursday with his campaign manager, Randy Dawson.

The Conservatives have taken pains to shield local candidates from the national news media during the campaign, preferring to bypass the Parliamentary press corps in favour of local reporters.

They've also strenuously sought to make inroads with the immigrant communities that were once largely enclaves of Liberal voters. Those communities could hold the ticket to a Conservative majority government -- especially in the suburban battleground ridings that surround Toronto.

Richardson is the latest in a long line of candidates who have landed in trouble for loose lips.

Most notably, Agriculture Minister Gerry Ritz caused a campaign uproar after The Canadian Press revealed last week that he joked about the deadly listeriosis outbreak.