Mana leader Hone Harawira says the Maori Party is in "terminal decline" and will be "dead" at the polls in 2014 if it doesn't change its ways.
Speaking on Firstline this morning, Mr Harawira said he has approached his former party with offers of reconciliation, without any luck.
"I have been approached by Maori Party members all around the country, asking me to come back," he says.
"But I can't come back the way it's set up, the way they're connected to National, the kinds of policies they're supporting at the moment."
Pita Sharples, 71, said last week he would lead the party into the 2014 election, instead of stepping aside for the younger Te Ururoa Flavell, 57. Co-leader Tariana Turia will be 69 in April.
"The leadership is really starting to show its age," says Mr Harawira. "Tariana's getting on to 70, Pita's already in his 70s – he'll be 73 next year. In this game, people are looking for strong, vibrant, challenging kind of leadership, and both of them are starting to show they're wanting to slow down, when in fact Maoridom – and Maori people – are very much a younger, more vibrant, more active people."
He says the party's association with National is a threat to its long-term future.
"When I was there the Maori Party had a membership of 24,000," he tells Firstline. "At their last AGM they recorded a membership of 600. They're in terminal decline."
Despite his suspicion of Labour, which he says has moved "to the centre and more and more to the right and away from the poor and the dispossessed", he says Mana would be comfortable joining them in a coalition of the left.
"I'm comfortable working with the Greens – I've had a couple of chats with [Labour leader] David Shearer, and I look to increase those over the next year or so.
"Clearly we are on that side of the camp, and I'm comfortable being there."
Mr Harawira says his party will have nothing to do with National, which is causing "huge damage to Maori communities".
"Is there an opportunity for us to bring the Maori Party and the Mana movement together? … I think Maori people generally are saying to the Maori Party – and the membership dropping from 24,000 to 600 – is sending a very clear signal: get away from National, or you're dead come 2014."