The Conservative government cut funding to a federal immunization program even as public skepticism about vaccinations was growing in the midst of the swine flu outbreak in 2009, documents show.

The Conservatives have cut funding to the program -- an initiative that educates Canadians about the importance of immunization -- by a total of 23 per cent since 2006.

On Tuesday, Liberal Leader Justin Trudeau took a swipe at Prime Minister Stephen Harper for the spending reduction as dozens of North American communities find themselves grappling with measles outbreaks.

"Will he stop his self-promoting, partisan government ads and invest instead -- now -- in a campaign that encourages parents to vaccinate their kids?" Trudeau said during the daily question period.

The government has been "very clear" that Canadians should seek vaccines against a host of illnesses, Harper replied.

A 2006 report on the Public Health Agency of Canada showed the government had committed $10 million to the federal immunization program. By 2014, that number had fallen to about $7.6 million.

By way of contrast, newly released figures reveal that the Conservatives spent more than $7 million on a 12-week anti-drug advertising campaign that ended in January.

Trudeau suggested last year that the Health Canada campaign was meant as an attack on his support for legalizing marijuana, an allegation that was roundly denied by Health Minister Rona Ambrose.

A week ago, Ambrose chided Canadians who have failed to vaccinate their children.

"I find it really irresponsible," Ambrose said in Vancouver.

"If you don't immunize your child and you send them to school potentially ill, or expose another child who may be more vulnerable than your own is, at even a greater risk ... that's what concerns me the most."

But the government's own polling suggests that since 2006, Canadians were growing increasingly skeptical about vaccinations. That was especially true during the 2009 H1N1 scare, when some respondents expressed concerns about the safety of the swine flu vaccine.

"You hear in the news that healthy children die from this, so that is the fear," one respondent told Decima Research. "You don't want your child to be part of that statistic."

A 2012 audit of the immunization program also found that it was short-staffed, and questioned whether vaccination education efforts were proving successful.

The audit recommended a "systemic and comprehensive review" of the program.