A spokeswoman for Mr Key said: "The Prime Minister has attended a number of functions for the Maori Party and the other parties we have relationships with. It doesn't signify any deal, it simply illustrates a good relationship with parties we work with."
She said the wording of the invitation was a matter for the Maori Party but Mr Key was comfortable with it. "At fundraising events the PM often changes seats in order to meet as many people as possible."
The Maori Party is also defending the arrangement.
Maori Party president Naida Glavish said there was a close relationship with the National Party, which sought out a coalition deal in 2011 when it didn't need to.
"We were having a fundraiser and asked if he would be a dinner speaker. That's all it was. That just signifies to us the generosity of John Key."
She said it did not shut out coalition options this election. "As far as the Maori Party and National, we are sitting at the table of government. If someone else was the government, we would still be asking to sit at the table of government."
Ms Glavish confirmed seating was changed to move Mr Key around. "We can't control who he speaks to after the dinner." Asked if the $5000 "donation" price tag was a lot of money, she said: "It is for some."
"That is the sort of fundraising we need to do to financially prepare ourselves for the upcoming election."
The minimum $75,000 raised compares well against the $100,000 raised by the Maori Party for the 2011 election.
The meeting was exposed by Maori Television's Native Affairs show, which last night showed footage of guests arriving.
Mana Party leader Hone Harawira was stunned to hear of the dinner after comments criticising a proposed Mana-Internet Party deal.
"Our dealings with [tycoons Kim] Dotcom and Gareth Morgan have been very open and we haven't received a cent."
