Ontario Premier Kathleen Wynne says she will testify at the trial of two Liberals facing bribery charges under the Election Act.

The trial for Pat Sorbara, the premier's former deputy chief of staff, and Liberal fundraiser Gerry Lougheed, is set to begin in September.

The pair is accused of offering a would-be candidate a job or appointment to get him to step aside in a 2015 by-election in Sudbury, Ont., for Glenn Thibeault.

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At the time, Thibeault was a New Democrat MP. He is now the energy minister.

Sorbara and Lougheed both deny the charges.