TORONTO -- Ontario's Progressive Conservatives served notice Thursday they intend to "vigorously defend themselves" against a $2-million libel suit filed by Premier Kathleen Wynne, calling it an attempt to muzzle the Opposition.

"We're not backing down," said PC energy critic Lisa MacLeod. "We're going to continue to ask the tough questions."

The suit stems from Opposition Leader Tim Hudak's comments suggesting that Wynne "oversaw and possibly ordered the criminal destruction of documents" related to the $1.1-billion cancellation of two gas plants prior to the 2011 election.

"The public knows what this is; it's an attempt to silence the Opposition, and we're not going to be silenced," said MacLeod, who was named in the libel suit along with Hudak and the PC Ontario Fund.

"There is a lot of support for Tim and I because we're asking the tough questions, trying to get to a billion-dollar scandal and why that happened."

Lawyers for the Tories filed a notice of intent to defend in the libel suit, saying the Conservatives don't believe any of their comments "constitute actionable defamation" of Wynne.

"All of the statements about which your client complains are clearly within the recognized privileges protecting freedom of speech, particularly where it concerns matters of public importance within a necessary and vital public debate," wrote Robert Rueter of Rueter, Scargall, Bennett on behalf of the Conservatives.

Wynne claimed in an open letter March 30 that Hudak knew his accusations about her alleged involvement in the wiping of computer hard drives were false and not supported by evidence, and demanded he apologize and retract the comments.

But the Tory notice of intent to defend said it was Wynne's "deliberate release" of her open letter that "attracted and intensified media coverage" of the very statements about which she is complaining in her libel suit.

"The fact that the premier has made this a media issue has ensured that the comments and the tweets would have received a much larger audience than had they just been said in the halls here at Queen's Park," said MacLeod.

One of the comments Wynne complained about in her suit was a tweet from MacLeod comparing the premier to disgraced former U.S. president Richard Nixon, something the Tory energy critic was "not at all" afraid to repeat Thursday.

"Kathleen Wynne apparently doesn't like being compared to U.S. presidents," said MacLeod, who was immediately asked which president. "Richard Nixon."

The notice gives Wynne until April 29 to drop the libel suit or the party will follow up with a statement of defence requesting the case be dismissed, but the premier's office said it's Hudak and MacLeod that can end the legal action with an apology.

"Mr. Hudak, Ms. MacLeod, and the PC Party still have an opportunity to do the right thing, apologize and retract their comments," said Wynne's press secretary Zita Astravas.

"If they do, this action will not be pursued further and damages will not be sought."

The libel suit is playing out at the same time that a legislative committee is holding public hearings into the Liberals' decisions to cancel gas plants in Oakville and Mississauga, and an OPP probe into deleted emails on the energy projects.

Provincial police are considering possible breach of trust charges against a top aide to former premier Dalton McGuinty, who allegedly gave an outside tech expert access to computers in the premiers' office.

Police allege McGuinty's chief of staff, David Livingston, gave access to the boyfriend of another senior Liberal in McGuinty's office to 24 computers in the premier's office in February 2012.

Experts have only been able to recover data from four of the 24 hard drives that they seized, which show a special password was used Feb. 6 and 7, 2012. They can't say yet if the other hard drives were accessed with the special password after Wynne became premier Feb. 11, 2012, but it was valid until March 20.

Wynne maintained Livingston never worked for her, only for McGuinty.