Potato growers are using 50 tractors to protest outside the McCain factory at Ballarat, in central Victoria, over contract negotiations.

The 100 growers have vowed to remain outside the plant until the company meets their demands for a better potato price.

They have been in talks with the Canadian-owned company for several months.

Growers spokeswoman Laura Bowles says the protest is an 11th-hour bid to get a better offer.

"McCain haven't given the growers a fair go this year," she said.

"Growers are completely fed up and this is sort of a last-ditch effort to draw attention to their cause."

McCain Potato Growers Association president Dominic Prendergast says they will not leave until the company responds.

"We'll stay here for a few days - at the worst a week, two weeks. We'll stay here as long as it takes until the company gives us a positive result," he said.

Federal independent MP Bob Katter has called for national action on the price farmers are paid for their produce.

Mr Katter is confident the potato growers will win, and gave the company a warning.

"You're going to lose and you're going to damage your brand name very very badly. Get a bit of sense. Act responsibly," he said.

"You know in Australia in the past year, corporations have a bigger picture than just their company profits."

McCain Foods says it is disappointed with the attitude of the growers.

It says contract prices have been agreed to in New Zealand, Tasmania and South Australia, but the Ballarat farmers are holding out until the last moment for higher prices.