OTTAWA — Prime Minister Justin Trudeau of Canada has been trying for weeks to shift the country’s attention from accusations by his former justice minister that his government improperly pressured her on a criminal case.

On Wednesday, members of his party helped him do that by blocking the minister from testifying again about the matter before a parliamentary committee.

Mr. Trudeau’s opponents immediately cried foul.

“What does this say to Canadians?” said Tracey Ramsey, a member of the New Democratic Party. “That they have something to hide.”

The committee is controlled by Mr. Trudeau’s Liberal party. Liberal committee members did not speak with reporters.