National Party leader John Key says it's time for the Prime Minister to go to the polls, so the public can have its say on the Winston Peters controversy.
Mr Peters stood down last week as Foreign Affairs Minister after the Serious Fraud Office began an investigation into the party. He is also the leader of the New Zealand First party.
New Zealand First has admitted breaching electoral law by not declaring a $50,000 payment from the Spencer Trust in 2005.
Documentation shows the first payment it received was $25,000 from businessman Sir Robert Jones in August that year. Records show that money, along with another $25,000 from other sources, was paid to New Zealand First.
The Spencer Trust has also said it gave money to New Zealand First in 2006 and 2007, but will not say how much.
At the launch of National's latest billboard on Wednesday, Mr Key said the actions of Mr Peters and Helen Clark should be put before the court of public opinion.
"She's been in this scandal for the last six months. She knows that there's been problems and she's been happy to just keep the New Zealand public in the dark about that.
"Frankly, I think we're at a point now where we're never going to get a straight answer from Helen Clark, we're never going to get a straight answer from Winston Peters and the public are over it.
"I think we should just have an election and get on with it."