Former Nationals minister Luke Hartsuyker will retire from federal parliament at the next election.
The NSW MP was vocational education and skills minister in the Abbott government, before holding junior positions under Malcolm Turnbull who dumped him from the frontbench earlier in the year.
"I am sure that his efforts as a minister and as a reliable local member will always be remembered, just as his affable presence, calm experience and optimism will be greatly missed," Prime Minister Malcolm Turnbull said in a statement.
Mr Hartsuyker's retirement has fuelled speculation of a comeback by former independent MP Rob Oakeshott.
Mr Oakeshott contested Cowper at the 2016 election, slicing the Nationals' margin to less than five per cent.
He told the Port Macquarie News he had not made any announcement "at this stage", but was concerned the electorate was "drifting" in terms of leadership, education, health and community services.
"The frustration in our area is that while we are growing and ticking along, we could be doing so much better," Mr Oakeshott said.
Nationals leader Michael McCormack and deputy Bridget McKenzie paid tribute to Mr Hartsuyker's 17 years in parliament.
"The people of the Cowper electorate put their faith in Luke Hartsuyker and he took their fight to Canberra," they said in a statement.
The Nationals leadership said he contributed to the work for the dole program, market access for farmers, and country of origin labelling.