Mayo vote environmental message - Greens

The Greens candidate for Mayo, Lynton Vonow, says the weekend poll in the Adelaide Hills-based electorate has sent a strong message to the major political parties.

Mr Vonow trails Liberal candidate Jamie Briggs by 3,265 votes on a two-party preferred basis.

There has been a 10.5 per cent swing away from the Liberals and Labor did not contest the poll, needed because of the retirement from politics of former foreign minister Alexander Downer.

Mr Vonow says the Liberals and Labor should treat the vote as a wake-up call.

"Not to take seats for granted and not to see this as business as usual," he said.

"The people of Mayo are recognising that the Greens are here.

"They're liking what they're seeing. They're liking that we're sticking up for the environment and they're recognising that the environment is of major concern and a priority."

The Liberals have claimed victory in the by-election but the Greens are not conceding until all votes have been counted.

Mr Briggs says water concerns will be a priority for him.

"There are big issues, nothing bigger than the river [Murray] and the lower lakes so I know the depth of feeling in the electorate about the river and I'm very keen to get into Federal Parliament and do the best I can to represent that issue," he said.