Coalition senator Ian Macdonald has moved to save his Senate seat by urging voters to ignore his party's instructions this election, and instead vote below the line.

Key points: Senator Ian Macdonald is urging Queensland residents to vote for him below the line

Senator Ian Macdonald is urging Queensland residents to vote for him below the line Voting for the LNP above the line means the party's preferences dictate who gets the Senate spot

Voting for the LNP above the line means the party's preferences dictate who gets the Senate spot The move follows the lead of Senate candidate Jim Molan, who was also relegated to an unwinnable position

Last year, the north Queensland Liberal-National senator was relegated to the unwinnable fourth spot on the LNP's Senate ticket.

Senator Macdonald said the decision came as a surprise, given his regional status as the only senator from north Queensland.

Three candidates from Brisbane — Paul Scarr, Susan McDonald and Gerard Rennick — were preferenced above him on the ticket.

"Naturally enough, I was disappointed," Senator Macdonald said.

"More importantly, people in the north were disappointed, and it was my intention when I did decide to leave Parliament, I'd be replaced by someone from the north."

Senator Macdonald has now moved to take matters into his own hands, sending out tens of thousands of letters and emails to Queensland residents.

It urged them to avoid voting above the line, where the party's preferences dictate who gains the Senate spot.

"Now I am seeking your help," the letter reads.

Gerard Rennick, Paul Scarr, party president Gary Spence and Susan McDonald. Rennick, Scarr and McDonald took the top three position's on the party's senate ticket for the next election. ( ABC News: Lexy Hamilton-Smith )

"For the next election, my party has placed me number 4 on its ticket after three Brisbane candidates, none of whom have any connection with local government.

"This means that voting above the black line on the Senate ballot paper for the candidates chosen by the party, will make it difficult for me to be re-elected to continue my fight for councils.

"I will, however, be one step closer to re-election if you vote below the black line for me on the Senate ballot paper [the big white one] giving me your number 1 vote."

The move follows the lead of his Coalition colleague Jim Molan, who was relegated to the unwinnable third position on the Liberal Senate ticket by the New South Wales branch in November.

His supporters have since printed his own how-to-vote cards, also encouraging New South Wales residents to vote below the line.