David Johnston says he is stepping down from his role as special rapporteur investigating foreign interference, effective no later than the end of June, citing the highly partisan atmosphere around his work.
The former governor general says in a letter to Prime Minister Justin Trudeau that his leadership of the government's probe into foreign meddling by China has not helped build trust in democratic institutions because of partisanship.
The appointment of Johnston, who says he will release a brief final report, has been contentious, with Conservative Leader Pierre Poilievre accusing him of being too close to Trudeau's family.
All opposition parties in the House of Commons have called for the government to call a public inquiry into foreign interference, but Johnston recently released a report recommending against that.
In his letter, he says a deep and comprehensive review of foreign interference should be an urgent priority for Parliament and reiterates his report's main finding that public hearings should be held.
He also says he encourages Trudeau to appoint a "respected person, with national security experience" to finish the work he started, and suggests he consult with opposition parties on who that should be.