Colin Craig is to give evidence at his defamation trial in the High Court at Auckland this afternoon.
The former Conservative Party leader is accused of defaming Taxpayers' Union director Jordan Williams.
Williams alleges Craig defamed him at a press conference, and then again in a pamphlet the former politician paid to have published and distributed to more than 1.6 million New Zealand households.
The allegation that Williams lied came after he took information given to him by Craig's former press secretary Rachel MacGregor to other Conservative Party members.
MacGregor had alleged Craig had sexually harassed her and Williams felt obligated to warn the other party members, despite her telling him not to disclose the information.