The High Court has rejected a bid for leave to appeal against a ruling in the genetic modification contamination case of West Australian farmer Steve Marsh.

Mr Marsh lost organic certification over most of his land at Kojonup after genetically modified canola blew over from his neighbour's farm in 2010.

He went to court, seeking more than $80,000 in compensation, but the Supreme Court dismissed the case in 2014.

The court found neighbour Michael Baxter had not acted negligently and could not be held responsible just for growing a GM crop in a conventional way. It also awarded Mr Baxter costs.

Last year it was revealed Monsanto had contributed to Mr Baxter's costs while Mr Marsh's campaign had been supported by the Safe Food Foundation.

Mr Baxter said he had no relationship with Mr Marsh any more.

Mr Marsh sought leave to appeal to the High Court, but it was dismissed this morning.

Today's decision means Mr Marsh has no further avenue of appeal.

'We lost our income for three years'

Mr Marsh said he was very disappointed, and described the judgement as extraordinary.

"It's a pretty straightforward case," he said.

"We lost our income, practically half our growing income for three years, but it appears that we can't claim compensation for that, it's extraordinary."

Mr Marsh said while it would be extremely difficult to ever rebuild a relationship with Mr Baxter, he would continue to farm in Kojonup.

"I will try and hang onto our farm, it is our business and we will try and do the best we can," he said.

"Organic farming is growing.

"I think that this case has highlighted that more than ever and issues about food and its safety and how we produce it," he said.

Mr Marsh said the court case had cost millions of dollars, but it was an important issue for the organic industry.

"I think we have to stand up for what we believe is right," he said.

"This issue is a very contentious issue, and it still will be long after this case is gone.

"But consumers should have the right to choose.

"Our case may be the first, but I don't believe it will be the last," he said.

'We could have had a chat over the fence', Michael Baxter says

Outside the court, Michael Baxter said he was relieved about the result, after a process he described as "six years of rigamarole".

"Like I said last time I came out of the court, it could have been avoided, we could have had a chat over the fence and this should have never got this far," he said.

"There's been a lot of money spent on the all the lawyers and everybody else to no avail really.

"This is the end, they can't go any further so this is the end of it and we are all really relieved," he said.