There is nothing wrong with ministers accepting hospitality from the Government's banker Westpac, and it won't have any bearing on the decision that will follow a competitive tender process for the contract, Prime Minister John Key says.

The Green Party today released the results of a series of written questions to Government ministers over their relationships with Westpac.

Nine ministers said they had accepted corporate hospitality from Westpac in the past year, including box seats at the rugby sevens, dinner at the White House restaurant in Wellington, and tickets to rock concerts.

Thirteen ministers said their staff had accepted similar hospitality from the bank.

Green Party co-leader Russel Norman said the ministers accepting personal gifts from Westpac created a potential conflict of interest while the Government was reviewing its banking.

"The fact that so many ministers had staff who also accepted Westpac's largesse is disquieting, given the central role of ministerial staff in influencing the decisions of their busy ministers," he said.

Dr Norman called for a competitive tender for the master banking contract, and for the Cabinet manual to be more explicit about accepting gifts.

Mr Key told reporters the Greens didn't have any legitimate concerns.

"The Government has opened the contract to a competitive tender for the first time in 20 years," he said.

"That process will go through normal procedures...Treasury will make the final decisions."

Mr Key said ministers and MPs who accepted gifts of hospitality from any organisation, above a certain level, had to disclose it in their register of pecuniary interests.

A spokesman for Finance Minister Bill English said the implication that ministers had been influenced by the bank's hospitality was wrong.

The Government had negotiated ongoing contractual price reductions for its banking service since 2005, and last year stated its clear intention to run a competitive procurement process for government banking designed to achieve value for money.

"Officials have already begun scoping work on that process, and this will be the first time in over 20 years the Government's master banking contract has been opened to a competitive process," the spokesman said.

Westpac's media relations manager Chris Mirams said the bank's corporate hospitality programme was to build and maintain relationships.

"Invitations are extended to a broad range of key stakeholders, including members of both sides of the House, without prejudice or expectation," he said.