Speaker of the B.C. legislature Darryl Plecas has hired Wally Oppal as a second special adviser, as questions continue to swirl around the extraordinary investigation and suspension of two of the legislature’s top officers.

The appointment was revealed Thursday afternoon by Plecas's first special adviser, Alan Mullen, who offered little in the way of explanation except to say the former attorney general will be providing advice on legal matters.

"We could not be more honoured and pleased that Justice Oppal has agreed to come on as a second special adviser, and we look forward to meeting with him tomorrow morning," Mullen told reporters in a brief statement.

Oppal told CTV News he looks forward to assuming the role, and said he may have more to say on Friday.

Hours earlier, Plecas came under scrutiny from his former party, the BC Liberals, who said the Speaker recently suggested Mullen could temporarily fill the role of sergeant-at-arms – one of the posts vacated Tuesday when two seniors officers were suddenly suspended from their duties.

Opposition house leader Mary Polak said the decision to remove Clerk of the House Craig James and Sergeant-at-Arms Gary Lenz was discussed at a meeting Monday night between her, Plecas, a lawyer and the NDP and Green house leaders.

An affidavit signed by Polak says Plecas "stated his wish" that Mullen be appointed acting sergeant-at-arms, an interim position. Speaking to reporters Thursday morning, Polak called the suggestion "not appropriate."

"He expressed the wish and was immediately cut off and told no," Polak said.

Mullen was hired by Plecas, and his duties included investigating the two senior officers before the files were handed off to the RCMP. At a news conference Wednesday, Mullen referred to himself as Plecas's friend.

Asked about the BC Liberals' concerns Thursday, B.C. Premier John Horgan said the investigation into James and Lenz remains "the core issue here at the legislature."

"The more important question is how quickly can we see resolution to the RCMP investigation," Horgan said.

Details about the allegations involving the seniors officers remain the biggest mystery in the capital this week.

Polak said no specifics were discussed at Monday's meeting, but the house leaders were told special prosecutors had already been appointed in the case.

That information alone was enough to justify Tuesday's unanimous vote to suspend James and Lenz from their positions, she added.

"Regardless of what other information the Speaker or others may have had, the house leaders being advised that specials prosecutors had been appointed meant that the appropriate action was the motion," Polak said.

On Tuesday, the government revealed James and Lenz are the focus of an ongoing RCMP criminal investigation, the details of which are being kept firmly under wraps. Authorities haven’t even confirmed which RCMP unit is handling the probe.

One of the few pieces of information shared with the public is that an investigation began internally in January, and was prompted by concerns from Plecas.

The RCMP was only called to investigate in September, and two special prosecutors were assigned to help police with the case in October.

"As the months went on, we gathered more information, and that just got passed off," Mullen told reporters Wednesday.

Opposition leader Andrew Wilkinson said he has concerns about the way the probe was conducted without the legislature's knowledge, and about Mullen's qualifications for the task.

"A seven-month investigation was being conducted by someone with no legal training or policing experience," Wilkinson said.  

The BC Liberals have had little love for Plecas since he agreed to serve as Speaker last year, preventing the NDP from having to put up one of its own MLAs and strengthening the party's frail minority government.

Plecas, who was then a Liberal MLA, was promptly kicked out of the party.  

With files from CTV Vancouver's Jon Woodward