Senior bureaucrats warned the Harper government that imposing a visa on Mexican travellers would overload Canada's diplomatic capacity.

The deputy ministers of Foreign Affairs and International Trade offered that assessment in a July 2009 briefing note to then foreign affairs minister Lawrence Cannon.

The memorandum, obtained by The Canadian Press under the Access to Information Act, was written by deputy ministers Len Edwards and Louis Levesque. The document highlighted "most notably the serious operational issues and challenges at our posts in Mexico as they prepare to become Canada's largest visa processing operation in the world."

The missive arrived on Cannon's desk days before the government announced the new visa requirement on travellers from Mexico and the Czech Republic, designed to curb bogus refugee claims from the two countries.

Both countries retaliated by imposing a visa requirement on Canadian diplomats, and the Czech Republic recalled its ambassador.

The document highlights the department's trepidation in coping with backlogs because of a massive influx of visa applicants. At the time, some 266,000 Mexicans visited Canada annually, the sixth-largest source of tourists to Canada.

"Given the short time frame, the projects are challenging in every respect. Resources have been diverted from elsewhere in the world to provide the highest level of readiness possible, but the capacity created will not be sufficient for a period of time," says the memo.

Foreign Affairs and Immigration Canada were working to beef up staff, security and technology.

"This is being done on a best-efforts basis with staff and contractors working nights and weekends."

The note said it would take eight to 12 weeks to reach 40 per cent of the required capacity to process "priority visitors," and eight to 10 months to reach full capacity.

"The work is being done while operations are ongoing. … This is disruptive and difficult for staff and visitors."

Plans were under way for acquiring a new facility for 80 to 90 staff within 10 months.

"This is also a challenging objective, as it will provide the full capacity required to support the largest visa program in the world and is equivalent to opening an entirely new large-sized mission in a time frame that has never been achieved before."

Diane Ablonczy, junior foreign minister for the Americas, said last week Canada has set up a series of new processing centres that now meet the demand in Mexico for visas.

"Visa turnaround times are about eight days. Multiple entry visas, particularly for business travellers have been instituted," said Ablonczy, who returned from Mexico last week.

"I think overall, given our continued commitment to work on this situation, our neighbours in Mexico are reasonably satisfied with how things are being handled at the current time."

The two senior bureaucrats also urged Cannon to give a heads-up to his Mexican counterpart, Patricia Espinosa, and her cabinet colleague, Economy Secretary Gerardo Ruiz Mateos, to tell them the government's announcement was imminent, as well as his Czech counterparts.

However, a leaked U.S. diplomatic cable recently posted on the Wikileaks website said the American embassy in Mexico learned from a Canadian embassy contact that "the Mexican government was not warned in advance of this announcement."

The memo says Immigration Minister Jason Kenney informed the Czech government of the impending visa decision about two weeks before it was announced, on a trip to Prague in late June 2009.

The government defended its unpopular decision with statistics showing the number of Mexican refugee claimants had almost tripled to 9,400 from 3,400 between 2005 and 2009. After Canada lifted a visa requirement on Czech nationals in 2007, the number of Roma claimants jumped — from five in 2006 to 840 two years later.

At the time, Kenney blamed Canada's broken refugee system, which the Conservative government has pledged to repair.

Ablonczy said the Mexicans remain disappointed with the visa, but her counterparts gave her positive feedback about Canada's immigration reform efforts.

"There's a strong understanding of why that (visa) was necessary in light of our own legal system."

A spokeswoman for Kenney defended the visa requirements Sunday, saying the move has paid off.

"Asylum claims from Mexico decreased 90 per cent in 2010 compared to 2009," Ana Curic said in an email to The Canadian Press.

"That has saved taxpayers $400 million."