UPDATE | Butts wants to tell his side of the SNC story

Prime Minister Justin Trudeau's former principal secretary Gerald Butts is asking to testify on the SNC-Lavalin affair.

Butts has written the House of Commons justice committee, requesting to be called as a witness.

His request comes one day after former attorney general Jody Wilson-Raybould testified that she faced relentless, inappropriate pressure and even veiled threats from Trudeau, Butts, Canada's top public servant and the finance minister's office to politically interfere the criminal prosecution of the Montreal engineering giant.

Butts, who resigned last week, says he believes he has evidence that will be of assistance to the committee in getting to the bottom the affair.

He says he will need a short time to receive legal advice and compile relevant documents.

The committee is to meet behind closed doors later this afternoon to plot its next steps.