Gareth Morgan is set to challenge in court The Opportunities Party's (TOP) exclusion from Television New Zealand's multi-party leaders' debate, TVNZ says.
TOP does not meet TVNZ's criteria to be part of Friday night's debate because it is not already in parliament and it is not polling above 3 percent.
TVNZ head of news and current affairs John Gillespie said it would work through whatever arises.
But he said TVNZ stands by its debate criteria, which have been applied in the last two elections.
In 2014, the then-Conservative Party leader Colin Craig was successful in his court action to be included in TV3's minor party leaders' debate on The Nation.
In 2005, Peter Dunne and Jim Anderton won a similar action against TV3.