Labour has confirmed its top adviser Matt McCarten will stand down as Andrew Little's chief of staff.
Labour says McCarten will head to Auckland to run a new regional office.
It follows Newshub revealing that McCarten's staff were told there will be a "special announcement" later this week.
McCarten's departure is a major blow to the party with the chief of staff role deemed absolutely critical in the political sphere - it is the leader's strategist, gatekeeper and enforcer.
It leaves Little without a lieutenant and the party's Parliamentary staff without a leader with only about twelve months until the election.
When asked earlier on Monday if he would be chief of staff by the end of the week, McCarten declined to comment.
McCarten has been in the job for 18 months, originally taking the role under David Cunliffe's leadership before being re-appointed by Little.
McCarten is highly regarded for his political cunning and strategic skills and is one of country’s political maestros.
The former union leader was diagnosed with what he was told was terminal cancer four years ago and at one stage thought he had only a few months to live.
Labour is already lacking a chief press secretary after Sarah Stuart left the party several weeks ago.
Labour has struggled to settle on a chief of staff since Helen Clark's adviser Heather Simpson, who was known as 'H2' left after the 2008 election loss.
Labour has had at least five people in the role in that time, while John Key has had just the one - Wayne Eagleson.