Liberal MP Mark Holland, co-chair of the all-party public safety committee that has delved into the case of Maher Arar, says two people who had key public safety roles have declined to appear for questioning.

Margaret Bloodworth, the former deputy minister of public safety, and the Associate Deputy Minister of Public Safety William Elliott, who was also Paul Martin's national security adviser, were asked to appear before the parliamentary committee this week. Holland said they declined, saying they were too busy.

"We had called for the national security advisor to the prime minister and Minister Day's deputy minister ... so we could question them about what they knew and when they knew it, and suddenly we've just learned they're too busy, they're too busy to go before our committee," Holland said during an interview that appeared Sunday on CTV's Question Period.

"Now we have deputy officials and the security advisor who despite this file being as large and important as it is are saying they're simply too busy to talk to our committee."

Holland wouldn't go so far as to say they were told by the government not to show up, but said the decision is suspicious and questionable.

"There are important questions that have to be answered and the fact they're not making themselves available is simply unacceptable."

Holland has been demanding tough answers from Public Safety Minister Stockwell Day about how Maher Arar's case was handled by the RCMP, prompting Day to describe him as a "Perry Mason on steroids."

RCMP Commissioner Giuliano Zaccardelli stepped down from his position this week after contradicting himself on what he knew -- and when he knew it -- about Arar's deportation to Syria by U.S. authorities, who reportedly acted partly on the basis of false information provided by the RCMP.

In Syria, Arar was detained and tortured into falsely confessing he had links to al Qaeda.

When asked in the House of Commons, Day said he needed time to think about whether Zaccardelli still had the confidence of the government.

Shortly afterwards, Zaccardelli resigned from his post.

Holland said he is afraid misdeeds within the RCMP will be forgotten now that Zaccardelli has resigned, and said he will be pushing for witnesses to appear before the committee, which he co-chairs, in early January.

The House will likely break for the holidays on Wednesday, and is not scheduled to return until Jan. 29.

"My biggest fear is that we say okay, the commissioner is gone, this thing is done. It most certainly is not done."

Stockwell Day also appeared on Question Period on Sunday, though he didn't address Holland's allegations that the government put pressure on the witnesses not to show up at the hearing.

Day said he didn't pressure Zaccardelli to resign -- one of the questions Holland put to him when he appeared before the committee.

"When the commissioner wanted to address what he said were some inconsistencies, that was a point of interest for sure. And then when we saw the nature of those contradictions, that gave considerable pause, and that's why I said, and the prime minister said, that we wanted some time to look at those contradictions," Day said. 

"And it was in those ensuing days of last week that the commissioner made his decision to resign."

Day said Zaccardelli's replacement will be chosen carefully. He said he has told members of the standing committee on public safety that he is open to their suggestions. He will also give weight to the soon-to-be-released second half of Justice Dennis O'Connor's report on the Arar affair and his recommendations on implementing oversight measures for the RCMP.

"We are going to do this carefully," Day said.

"It won't be a long time but we want to do it the right way, one that continues the confidence that Canadians have -- and Canadians still do have great confidence and it's well-founded in the RCMP because those men and women are doing a great job."