The CAQ said it has a direct interest in fighting alleged corruption in the awarding of public contracts in the construction industry.
During last month's election campaign, CAQ leader François Legault focused many of his promises on abolishing corruption and collusion in Quebec's provincial government.
Participant status allows the party's lawyer to cross-examine witnesses.
When filing its request, the CAQ, which now holds 19 seats in the National Assembly, said it helped pressure the government to launch the inquiry.
Chief prosecutor Sylvain Lussier disagreed with the CAQ's request. He said the party should only be granted intervenor status – something Québec Solidaire, the sovereigntist party, was awarded.
The Parti Québécois was given participant status because it was one of the parties in power in the timeframe the commission is studying.
The Liberals, on the other hand, have not asked to participate.Suggest a correction