One of Australia's biggest political donors, the National Australia Bank, has quietly announced it will stop giving money to political parties.

According to the bank's policy statement on political donations, the board of directors "resolved in May 2016 that the making of any political donations would cease with immediate effect".

All of Australia's major banks, including ANZ, Westpac and the Commonwealth, give generously to both sides of the political aisle. NAB's move, if honoured, would make it the first to eschew the practice.

"NAB does not make donations or contribute funds to any political party, parliamentarian, elected official or candidate for political office," the policy document states.