"Not only is it bullying but it's actually stopping freedom of speech," she said.
"This is why we need change in Hawke's Bay."
Tremains director Simon Tremain said he was also frustrated by the decision.
While it was a condition in the site lease contract that the airport company needed to approve all signs that Tremains put up, it was the first time the airport had acted on that condition in the four years since the lease began.
"If [the sign] was rude, obnoxious or was something that didn't agree with the airport then of course it should come down but in this case it's a political game they're playing," he said.
"We will play ball. If they want it taken down, we will take it down."
Airport chief executive Nick Story said: "The airport is publicly owned infrastructure. It's therefore inappropriate that airport land be used for political advertising or campaigning."
Mr Dalton said because the airport company was 26 per cent owned by Napier City Council, 24 per cent by Hastings District Council and 50 per cent by the Crown, "they should be entirely neutral and stay well out of it, and by hosting such a site they're anything but".
Hastings Mayor Lawrence Yule said his council did not have a view on the issue, which was a matter for the airport company.
While it was a shareholder in the business "controlling what's on a billboard is not the level of input that my council would want to be involved in".
"If something was culturally offensive we may have a view of it but, in terms of people using the democratic process and actually paying for the privilege, I don't think our council would have any issue with it."
The sign-written vehicles of local MPs Stuart Nash and Craig Foss are often prominently visible in the airport's carpark while they are out of town, and Mr Yule said that raised the question of where the line on political advertising should be drawn.
"If A Better Hawke's Bay put their caravan in the carpark, would that be any different?"
