Qld MP sets his resignation date

Toowoomba South MP John McVeigh will resign from Queensland parliament on April 29 to give the government time to organise a by-election.

A Queensland MP trying to switch to federal politics will resign from his state seat in two weeks. (AAP)

Tens of thousands of southeast Queensland voters will likely be forced to head to the ballot box twice in the space of a few weeks.

Toowoomba South MP John McVeigh will resign from state parliament on April 29 after winning Liberal National Party preselection for the federal seat of Groom, which will be vacated by retiring former minister Ian MacFarlane.

Opposition Leader Lawrence Springborg says the definite resignation date will give certainty for voters and give the government more than two weeks' notice to prepare for a by-election in Toowoomba South.

Mr Springborg said that date meant a by-election could be held in the seat of more than 33,000 voters as early as May 28.

If Prime Minister Malcolm Turnbull makes good on his threat of a federal double-dissolution election on July 2, it means the electorate will need to vote twice in the space of a few weeks.

The looming polls also come after Queensland's local government elections were held in mid-March.

Mr Springborg said there would be no reason for Premier Annastacia Palaszczuk, who's on an overseas trade mission, to hold the by-election after the federal poll.

"There can be no justifiable reason, other than silly political games, for the premier to delay the calling of a by-election," he said.

"She clearly knows the time frame now and what we can have is a new representative for the people of Toowoomba South sworn in the parliament by the middle of June with an election at the end of May."

Mr Springborg said neighbouring LNP MPs Trevor Watts and Pat Weir would assist Toowoomba South constituents while the electorate was without an MP.

Mr McVeigh rejected Deputy Premier Jackie Trad's assertions he'd already "clocked off", saying he would be busy finalising business in his electorate over the next two weeks.

"I look forward to continuing with constituent matters over the next two-and-a-half weeks," he said.

Both major parties are yet to announce candidates for the by-election.