A former member of the Conservative Party is promising to reveal evidence of what he calls serious offences by Colin Craig.

John Stringer has announced he's holding a press conference in Christchurch this afternoon.

He's promising to provide documents, emails, letters, and photos, along with people who are prepared to testify in court about the so-called offences.

There's no word yet on what those serious offences are.

Mr Craig has previously faced accusations of behaving inappropriately towards a former staffer.