The shroud of secrecy surrounding the residency requirement for Canadian senators just got a bit thicker.

Prime Minister Stephen Harper has refused to answer repeated oral questions about the process he follows to ensure that an individual meets the constitutional residency requirement for appointment to the Senate.

So NDP ethics critic Charlie Angus figured his best chance at getting an answer lay in placing a written question on the order paper of the House of Commons — a procedural manoeuvre to which the government is obligated to give a detailed response.

No go.

Angus' question elicited this terse reply from Harper's parliamentary secretary, Paul Calandra: "The government does not comment on matters before the courts."

Calandra was referring to the fraud, bribery and breach of trust trial of Mike Duffy, where the suspended senator's qualifications to represent Prince Edward Island when he lived primarily in Ottawa is a pivotal issue.

NDP MP 'pretty shocked' by response

"I was pretty shocked (by Calandra's response) because normally an order paper question is done without political interference, it's straight-up answers, the government has to respond," Angus said in an interview.

"They're actually interfering with the work of Parliament now in order to suppress something that should be a fairly straightforward answer."

The government's respect for the courts seems to be selective, Angus added, noting that Harper, his ministers and backbenchers have not been reluctant to comment on other matters before the courts, when it's suited their political interests.

For instance, Harper called it "offensive" to cover one's face while taking the oath of citizenship even as his government launched an appeal of a court ruling allowing a woman to wear a niqab during the citizenship ceremony.

Just last week, Conservatives conveyed their disappointment that a judge had rejected the government's bid to keep convicted terrorist Omar Khadr behind bars.

The Constitution requires that a senator be resident in the province he or she is appointed to represent.

In his written question, Angus asked about the procedure followed for each of the 59 Senate appointments made by Harper, not singling out or even mentioning Duffy.

Senate blocking release of residency review

He asked if the government verified that each individual met the residency requirement and, if so, to explain precisely how that verification was done.

And he asked the government to produce details of each senator's residency verification.

The government's brushoff follows the Senate's refusal last week to allow an internal review of senators' residency to be entered into evidence at Duffy's trial.

The upper house has claimed parliamentary privilege to prevent the report being made public but that has been challenged by Duffy's lawyer.

Other documents filed in court last week suggest that top Conservative senators worked behind the scenes with Harper's office to kill the internal residency review, prompting senior Senate administrators to threaten legal action if the report was not released.