Duceppe was appointed by the Parti Quebecois government last week to lead a commission whose role will be to fight the federal government over changes to skills training.
Provincial Liberals and the Coalition party insist Duceppe is only there to advance the sovereigntist agenda.
Coalition spokesman Gerald Deltell says the government should have found someone more inclusive than Duceppe.
Deltell says the rest of Canada is not going to be swayed to Quebec's argument by someone who railed against the federal system for the last 20 years.
Liberal Kathleen Weil says she believes Duceppe is mainly present to show how federalism doesn't work and isn't likely to build a consensus with the rest of the country.
The provincial government is to provide more details on Duceppe's mandate on Wednesday.