While many senators are talking about the expense scandal this week, one senator from Saskatchewan has remained mum about a separate controversy involving an off-shore trust.

Saskatchewan Senator Pana Merchant isn't answering questions from CBC News about what, if anything, she disclosed to the Senate ethics officer about a trust set up by her husband, prominent class-action lawyer Tony Merchant.

Documents obtained by CBC show Pana Merchant was listed as a beneficiary to a $1.7 million trust set up in the Cook Islands, an off-shore haven in the South Pacific.

The information came from a huge leak of offshore financial information obtained by the International Consortium of Investigative Journalists.

CBC's report about the trust came out on April 3. Under Senate rules put in place in 2005, Pana Merchant would have been required to confidentially declare that she was a beneficiary of the trust to the Senate's ethics commissioner.

CBC asked Pana Merchant to talk about the trust and whether or not she disclosed it, in confidence, to the Senate ethics officer — but after seven weeks, she hasn't answered the questions.

Meanwhile, when Liberal Leader Justin Trudeau was asked this week if he's spoken to Merchant about the matter, he said he only wanted to talk about the $90,000 paid by the prime minister's former chief of staff to Conservative Senator Mike Duffy, who has now left the Tory caucus.

"Right now I am not talking about ethical lapse other than the extraordinarily serious one that the prime minister of this country committed," Trudeau said.

When asked again about Pana Merchant, Trudeau said he had not personally spoken to her. "I know the leadership of the Senate has engaged with her on the issue," he said.

Liberal Senator James Cowan, who is leader of the opposition in the Senate, says he spoke to Merchant last month.

"I told her that we have a Senate Code of Ethics that requires disclosure of some private financial information and that of your spouse to the extent you know it, so that she should have a discussion with the Senate ethics officer to make sure she was fully in compliance," Cowan said.

For its part, a spokesperon for the Senate ethics office says it can't comment on the individual circumstances of any senator.

Senators Duffy, Pamela Wallin, Patrick Brazeau and Mac Harb are the four members of the red chamber facing scrutiny over expenses.