But Mr Delahunty said he was sad to be stepping away from a job he loved.

"I feel a little bit down, probably because its been a great ride," he said. 

"I've enjoyed being the Member for Wimmera and then the Member for Lowan and the great community I've represented.

"In some ways I'm a little bit sad to leave, but it's the right decision and I'm very proud of the party because we've picked a great candidate - a very decent, hard-working woman who's now been supported by the Lowan electorate."

Across many parts of the state, the Nationals endured a disastrous election.

The ultra-safe seat of Shepparton was lost to independent Suzanna Sheed and Member for Morwell Russell Northe survived an double-digit swing to Labor to hold on.

Member for Western Victoria David O'Brien is set to lose his seat to a minor party, leaving the Nationals' party status in jeopardy.

Mr Delahunty said incoming member Emma Kealy's strong showing at the ballot box was crucial to the party's future.

"In some ways I felt the energy to keep going, but I felt it was time to move on and time to reinvigorate our party," he said.

"The party's selected a young lady from Edenhope and she'll be a great asset, not only for the Lowan electorate but also for the National Party."

Mr Delahunty said he was looking forward to spending time with family in retirement.

"It's been a difficult road because you don't have a lot of time with your family," he said.

"I've got seven grandchildren I'd love to catch up with. 

"I'll play a bit of golf, do a bit of travel but also just tidy up around the home - and get to own my home rather than just be a resident who moves in and out of the bedroom."

Mr Delahunty said the Wimmera-Mallee Pipeline was a major achievement during his time in parliament.

He nominated securing funding for Horsham Special School and Horsham College, and more money for agricultural research and health services in the electorate as other major advances for Lowan during his time.

"If you want to be crook in any country, the country to be sick in is Australia. We've got good health facilities and I'm pretty proud of being a part of the re-development of those," he said.

Mr Delahunty leaves with a rare affection from the Labor Party.

"I treat people the way I'd like to be treated - with respect," he said.

"We've all got our jobs to do. We've all got two legs, two arms and it's important to work with the other side.

"If I'm not happy with them I'll give them a chance. You've got to give them a chance."