Liberal MPs Kevin Lamoureux and Jim Karygiannis say there are more than 300,000 permanent residents whose citizenship applications are stuck in limbo.
They say people in some parts of the country face waits of up to five or six years for their applications to be processed.
Citizenship and Immigration Canada, on the other hand, says it takes 21 months to process routine Canadian citizenship applications.
The department says that figure is based on the time it took to process 80 per cent of all cases between July 1, 2011 and June 30 of last year.
The department says as of the end of September, there were 319,517 applications for grants of citizenship to be processed.
Figures provided by the department show there are also 619,780 people awaiting a decision on their applications to become permanent residents.
Alexis Pavlich, a spokeswoman for Kenney, says the Liberals are misrepresenting the number of backlogged cases.
"The Liberal critics have cherry-picked times from extraordinary cases in which CIC has had to undertake an investigation to determine whether an applicant has satisfied the residency requirements for citizenship," Pavlich said in an email.
"The current processing times for cases in which residency is not in question are much lower — only a few months higher than those we inherited from the Liberal party — but we are committed to lowering them even further."
Pavlich says the average processing time under the previous Liberal government in 2005 was 17 months — which she acknowledged has risen slightly in recent years.
"We inherited this system and got it down to 15 months," Pavlich said.
"During this time, however, we took a sober look at fraud and citizenship standards and since 2009 — when we started to fix the system — processing times have risen, but only slightly."