The man who's steered the Ministry of Foreign Affairs and Trade through restructuring blunders and the Malaysian diplomat saga is about to step down.

John Allen's resignation is set to be announced publicly next week, ahead of him taking up a private sector job.

Mr Allen has headed the agency since 2003.

He's been in the gun this year over an MFAT botch-up that allowed Malaysian High Commission worker Muhammad Rizalman bin Ismail to use his diplomatic immunity to leave the country, while facing sexual assault charges.

Mr Allen also weathered strong criticism over leaked restructuring plans and a subsequent witchhunt in 2012