The high-ranking Kathleen Wynne adviser at the centre of a criminal corruption investigation will not step aside.

As pressure mounted Wednesday for Patricia Sorbara to leave her job until the Ontario Provincial Police finish probing bribery allegations in the Sudbury by-election, the Premier stood behind her embattled aide.

The scandal has suddenly thrust one of the province's most powerful and publicity-averse political operatives into the spotlight. And the Liberals' steadfast defence of her has highlighted just how important Ms. Sorbara has become to the party after steering its winning general election campaign last June.

Story continues below advertisement

Police accuse Ms. Sorbara and Gerry Lougheed, a Liberal fundraiser and head of Sudbury police's civilian oversight board, of offering a government job to former Liberal candidate Andrew Olivier in exchange for dropping out of the by-election race.

"It is unacceptable to Ontarians that the Premier's deputy chief of staff and the chair of the Sudbury Police Services Board continue to hold their jobs and draw a public salary when they're under investigation by the OPP for attempted bribery," Progressive Conservative Opposition Leader Jim Wilson told a Queen's Park news conference Wednesday. "All eyes are on the Premier right now."

In court documents, police say Ms. Sorbara and Mr. Lougheed broke Criminal Code corruption provisions, which prohibit offering government appointments in exchange for political favours. No charges have been laid and the allegations have not been tested in court. The documents, including an information to obtain (ITO), were filed to get a production order for tapes of the conversations between Mr. Olivier, Ms. Sorbara and Mr. Lougheed.

While such political patronage is tacitly accepted by many politicians, it is relatively rare for it to come to light and spark a police probe.

The Premier's office swiftly rejected calls for Ms. Sorbara to leave.

"Our views on this matter are well known, any suggestion that anything was offered in exchange for any action is false," Ms. Wynne's spokeswoman, Zita Astravas, wrote in an e-mail. "It is common for an investigator to make an allegation in an ITO in order to obtain a production order. It is in no way confirmation that an offence has occurred."

Sudbury's police board also voted Wednesday to keep Mr. Lougheed as chair.

Story continues below advertisement

Ms. Sorbara is one of the country's top Liberals, running both the operational side of Ms. Wynne's office and the party's campaign apparatus.

She has a reputation as a tough taskmaster, focused on imposing discipline on the party and government. Taking over as campaign director in the late summer of 2013, Ms. Sorbara is credited by Liberal insiders with whipping the organization into shape ahead of last year's election. Among other things, she oversaw the adoption of Liberalist, a badly needed new database of voter information.

In a closed-door briefing last March, a record of which was obtained by The Globe and Mail, she told hundreds of rank-and-file party organizers she would use the data to check up on their canvassing.

"This will allow me back at central office to track your progress. That will result in the occasional phone call, I'm sure," she said at the weekend session at the Metro Toronto Convention Centre.

A Liberal lifer, Ms. Sorbara worked in former premier David Peterson's office in the 1980s and has been running campaigns for at least three decades. A 1986 news story identified her as the manager of the Liberals' successful effort in a York East by-election that year.

Ms. Sorbara joined then-federal leader Michael Ignatieff's staff in 2009 and served as second-in-command on his disastrous 2011 campaign. After that, she took a Queen's Park job as chief of staff to then-education minister Laurel Broten, before moving on to helm the party's election machine.

Story continues below advertisement

Despite this long history at the heart of the country's politics, Ms. Sorbara maintains a low public profile. She does not grant interviews or meet with reporters. Virtually her only public pronouncements come from her Twitter account, which mostly involves encouraging Liberal volunteers.

And if Ms. Wynne's loyalty to her seems rock solid, the dedication is mutual. "We're here because of our unwavering belief that we need Kathleen to continue as Premier in a Liberal government in Ontario," she said in that pre-election session last year. "We all need to pull together to match Kathleen's passion, her commitment and her incredible, incredible work ethic."