Key Points:

Maori Party co-leader Pita Sharples last night said National's deputy leader Bill English and the Maori Party chief of staff, Harry Walker, were present when National leader John Key agreed that the Maori seats would not be abolished without Maori consent.

Mr Key has denied giving any such assurance - most recently on Tuesday night during the TV One debate between Prime Minister Helen Clark and Mr Key.

Mr Key has denied it before, after Dr Sharples first made the claim in a Sky TV leaders' interview 11 days ago.

The issue not only goes to credibility but has the potential to put a strain on relations between the potential partners in Government.

National's policy is to abolish the Maori seats and Dr Sharples' statements suggest that Mr Key has already privately acknowledged that his party would agree to shift its policy - to keep the seats until Maori consented to their abolition.

Mr Walker last night said Dr Sharples' recollection of what was said was correct. Mr English could not be contacted.

Asked if he was absolutely certain that Dr Sharples' recollection was correct, he said "absolutely".

Dr Sharples expanded on the conversation he had had with Mr Key in a minor parties forum on Alt TV.

And he made it clear the Maori Party and National have had discussions on what it would take to work together after the election.

Asked about Mr Key's denials of the assurance over the Maori seats, Dr Sharples said: "I was not wrong."

Mr Walker said last night that Mr Key was clear in the meeting that National's position could be put on the back burner. He said the talks were part of relationship building talks the Maori Party had with both major parties and had been held in Dr Sharples' office at Parliament.

Deputy Prime Minister Michael Cullen said it was "more proof that John Key can't be trusted".

"John Key must come clean and clear up the confusion between the TVNZ leaders' debate and what he told Pita Sharples in private."