As Prime Minister Justin Trudeau comes under increasing fire for his handling of foreign meddling in Canada, he went on the attack on Wednesday, criticizing both the country’s main opposition party and Prime Minister Narendra Modi of India.

Mr. Trudeau, seeking to turn the tables on an issue on which he has been on the defensive, said on Wednesday that he had the names of Conservative politicians “who are engaged, or at high risk of, or for whom there is clear intelligence around foreign interference.’’

He then accused the Conservative leader, Pierre Poilievre, of failing to respond appropriately to the matter by declining to get security clearance so that he could be informed of the names of his party members under suspicion.

Under questioning later in the day, Mr. Trudeau acknowledged that he also had the names of members of his Liberal Party and of other parties who may have been compromised by foreign interference.

A lawyer representing the Conservatives accused the prime minister of “grandstanding” by singling out Conservatives.

Mr. Trudeau made the comments in Ottawa during a daylong appearance before an ongoing federal inquiry into interference by foreign powers into Canadian affairs.