The New Democrats are pressing for an unusual summer meeting of a parliamentary committee to clear the air over the auditing of charities for their political activities.
New Democrat MP Murray Rankin, the party critic for national revenue, wants the finance committee to convene before Parliament resumes in six weeks, calling the matter urgent.
Rankin has written to James Rajotte, Conservative chair of the committee, saying there are too many allegations that the audits are being used to silence opponents of the Harper government.
Since the spring of 2012, the Canada Revenue Agency has launched 52 audits of charities for their political activities, after the government ordered the special probe and eventually provided some $13.4 million for the initiative.
The first wave of audits in 2012-2013 targeted environmental groups who have opposed the government's energy and pipeline policies, but the initiative has since expanded to cover other groups who fight poverty, provide international aid and promote human rights.
Many of the groups say the audits have caused an "advocacy chill," preventing them from speaking out for fear of aggravating the auditors and potentially losing their coveted charitable status.
The Canada Revenue Agency refuses to provide the names of the groups being audited, citing confidentiality provisions of the Income Tax Act.
Rankin says public hearings before the finance committee would give besieged charitable groups a safe venue to speak out without appearing to provoke the tax agency.
"It wouldn't be as if they've gone to the press and spilled the beans," he said in an interview from his Victoria riding.
"We can't let this fester much longer. We've got to clear the air. It's bad for the reputation of the CRA and it's bad for the environmental organizations and other charities that are somehow under a shadow."
Last month, the New Democrats wrote to Revenue Minister Kerry-Lynne Findlay, asking her to order a special investigation into allegations of politically motivated audits of charities, headed by a retired judge or other neutral person.
Rankin says Findlay's office has not responded, and so he is now calling for the finance committee meeting.
Findlay has said in the past that the CRA works at arm's length from government, and makes its decisions about whom to audit independently, without her direction.
Canada's charities are permitted to devote up to 10 per cent of their resources to political activities, though the definition of what that constitutes is considered vague by some lawyers specializing in the area. Partisan activities, such as promoting a particular candidate for office, are forbidden.
The CRA has devoted at least 15 auditors to the political-activities audit initiative, and expects to carry out 60 such audits by 2016.