The revelation that federal meat inspectors were ordered to ignore carcass contamination at Alberta’s XL Foods plant reverberated on Parliament Hill Thursday, as opposition parties hammered the Conservative government over its handling of the E. coli crisis that sickened 18 people across Canada.

Agriculture Minister Gerry Ritz is once again under fire, this time over a Canadian Food Inspection Agency memo that instructed beef inspectors at the plant in Brooks, Alta., to ignore visible fecal and intestinal contamination on carcasses being processed for sale to Canadians.

The 2008 memo obtained by CTV News ordered inspectors to give extra scrutiny to meat being shipped for sale in Japan, however.

“Our number 1 priority is to ensure this standard is met with Japan eligible carcasses,” said the memo, written by a CFIA meat hygiene supervisor at the plant.

The CFIA reversed that policy only two weeks ago, when it sent a new memo telling inspectors to halt the meat production line and remove any spotted contamination on carcasses.

The news exploded in the House of Commons during question period Thursday, as the Conservatives fielded attacks over the CFIA’s 2008 directive. Some called for Ritz’s resignation, saying the minister has repeatedly failed to address food safety issues.

“That minister should have resigned months ago,” said NDP agriculture critic Malcolm Allen.

“We are talking about fecal material -- please don’t have me say the other word that begins with an ‘S,’” Allen said at a commons committee. “We’re talking about that on a carcass.”

Liberal MP Frank Valeriote said the RCMP should be called to “investigate what may amount to criminal negligence.”

Ritz and the CFIA denied that there is a two-tiered food safety system in place, saying meat being sold to Canadians was just as thoroughly inspected, but later in the production process.

“The de-contamination system for Canadian consumers, for all other export markets in the world, is further down the line,” Ritz said Thursday.

The president of the federal food inspectors’ union said that’s not true.

Bob Kingston said the meat is later put in a de-contamination shower, but the wash won’t remove feces from carcasses -- they have to be cut from the meat.

CFIA President George Da Pont, however, insisted that food safety is the agency’s “number one priority.”

Prime Minister Stephen Harper also defended the CFIA and his government’s response to the tainted meat crisis.

“CFIA confirmed the meat sold in Canada is just as safe as exports to other countries,” he said. “There are strict food safety standards in this country.”

With a report from CTV’s Ottawa Bureau Chief Robert Fife