The National Party is being called on to cough up a six figure sum to compensate broadcasters for not including GST in its election expenses.

The Green Party says figures from the Electoral Commission show public and private broadcasters wore losses of more than $100,000 because of the National Party's mistake.

The National Party admitted the blunder soon after the election, at the same time Labour was under fire for using the Prime Minister's budget to pay for its pledge card.

Now the Green Party is climbing into the controversy, saying final numbers from the Electoral Commission show the Nats left TVNZ out of pocket by more than $57,000.

The Radio Bureau was left $25,000 short, TV3 $20,000, while Prime and Sky TV missed out on about $10,000 between them.

A spokesman for the National party said the party offered to pay the money back at the time but is legally unable to do so. The Broadcasting Act did not allow for it.