They say the monitoring program used the public service for partisan ends.
"The issue is not that it is inappropriate for the government to monitor mainstream and ethno-cultural media," said Liberal Treasury Board critic John McCallum.
"Rather, it is that the Conservatives crossed the line when they used Canadians’ tax dollars to measure their performance at partisan events during an election campaign."
McCallum has written to Privy Council Clerk Wayne Wouters, essentially the country's senior public servant, to look into the program.
Documents obtained by The Canadian Press under access to information laws reveal that the Citizenship and Immigration Department spent nearly $750,000 over three years monitoring and analyzing ethnic media sources at home and abroad.
The reports, which ranked media reports from "very positive" to "very negative," included coverage of campaign events in cultural communities during the 2011 election. They also included six weeks of assessments of Immigration Minister Jason Kenney's media image in the spring of 2010, when the minority Conservative government was on an election footing.
A spokeswoman for Kenney called the Liberals' claims “completely baseless” and their letter of complaint “irresponsible.”
“Long-time Liberal MPs like John McCallum know that media monitoring continues during election campaigns, as per the Government of Canada policy,” Ana Curic said in an email.
Stephane Dion, Liberal critic for intergovernmental affairs, said the public service is supposed to provide professional and non-partisan advice.
"We fear that this situation very clearly endangers the public's perception of a professional, non-partisan public service in Canada," he said.
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