TORONTO -- British Columbia Premier Christy Clark is being asked to give her party's executive director some time off so she can testify about her involvement in the cancelled gas plants scandal in Ontario.

A legislative committee is seeking answers from Laura Miller about police allegations concerning the destruction of documents about two unpopular gas plants the Ontario Liberals cancelled at a cost of up to $1.1 billion.

Ontario New Democrat Peter Tabuns, who penned the letter to Clark, said he wants to make sure that there's no obstacle preventing Miller -- who Tabuns told reporters was a "person of interest" to police -- from returning to testify again before the committee.

"I would expect that the premier of B.C. respects rule of law and wants to see it respected by her staff and her colleagues," Tabuns said Friday.

Earlier this week, Clark said Miller "needs to make her own decisions" about whether to co-operate with the Ontario Provincial Police.

"She is a person of absolutely sterling character and she works incredibly hard for our party and for our province," Clark said. "She's a person of the utmost integrity and we're really, really lucky to have her in B.C."

Sharon White, president of the B.C. Liberal Party, echoed Clark's sentiments about Miller in a statement emailed on Friday.

"From here, it looks like they are gearing up for an election. I'm not going to comment on their politicking. I will say that if Laura decides to attend committee in another province, it will be her own decision," White said.

The controversy that's engulfed the Ontario Liberals for years -- even hastening the departure of former premier Dalton McGuinty -- appears to be spreading to the other end of the country.

Several senior aides who worked for McGuinty joined the B.C. Liberals after he stepped down in early 2013, including Miller, one of his deputy chiefs of staff.

She served on the B.C. Liberals' campaign team last year, along with McGuinty's former top strategist Don Guy. Miller and Guy have testified before the committee probing the gas plants scandal.

Ontario Provincial Police allege that Miller's boyfriend, Peter Faist, had access to computers in the premier's office and possibly deleted files just before McGuinty relinquished power.

They say computer experts cannot determine when 20 of 24 hard drives were accessed with a special password, which was valid for weeks after current Premier Kathleen Wynne was sworn in.

At the time, Faist was under contract to provide IT services for the government caucus and the Ontario Liberal Party. Both contracts have ended. David Livingston, McGuinty's former chief of staff, is alleged to have obtained the all-access password to the computers for Faist.

None of the allegations have been tested in court and Livingston's lawyer has said his client has broken no laws. Wynne insists none of the players had access to her office after she was sworn in on Feb. 11 last year.

One of the investigators, OPP Det. Const. Andre Duval, also told the committee on Thursday that Miller, Faist, Livingston -- a man currently under investigation for breach of trust -- and his aide Wendy Wai have declined to speak to police.

Miller's lawyer Brian Shiller said she didn't speak with the OPP because police couldn't assure her that her comments wouldn't be used against her in any proceeding.

"Laura was given verbal assurances that her constitutional rights would be protected but the investigator then refused to provide that assurance in writing and changed its position," Shiller said in a letter to the committee.

Miller is willing to assist the committee "in an atmosphere that respects" her constitutional rights, he said.

Tabuns said he expects Miller had "long discussions" with Faist and should be able to provide details about what happened in the premier's office.

"I think what we need to hear from Laura Miller is what she did, why she did it, when things took place and what her role was," he said.

"When we know that, we can comment further on exactly these virtues that (Clark) has alluded to."

Both Miller and Guy testified at committee last year about the events surrounding the Ontario Liberals' decision to cancel the two unpopular plants, one in the dying days of the 2011 election campaign that reduced them to a minority government.

They were questioned about emails that appeared to show an attempt to convince Speaker Dave Levac to change his preliminary finding of contempt against the government.

Miller told the committee that she and other unelected Liberals in McGuinty's office didn't try to pressure the Speaker to change his ruling against then-energy minister Chris Bentley, which stemmed from the government's initial refusal to release all documents the gas plants.

She testified the Liberals simply wanted the Speaker to know that they felt the Progressive Conservatives were unfairly targeting Bentley.

Levac did not deny the Liberals had attempted to persuade him to change his ruling, but said he never felt undue pressure when meeting with officials from any party.

After he refused to change his mind, McGuinty prorogued the legislature in the fall of 2012 and announced he would resign as premier, pre-empting the public hearings into the gas plants scandal.

The opposition parties say the Liberals scrapped the Mississauga and Oakville plants to try to save seats in the election and taxpayers are now paying the price.