The Senate has raised concerns about whether Parliament can return to sit before July 1 if the Prime Minister delays the federal election until May 25.

May 18 has been favourite for the election date in recent days. But speculation about a May 25 poll went into overdrive this week after the Australian Electoral Commission deleted a long-standing website reference that had said May 18 was the “latest possible date for a simultaneous (half-Senate and House of Representatives) election”.

This morning I screen captured and tweeted the text below from the AEC website. It was a statement on the last date for the coming Federal election. The reference has disappeared from the website at some stage today. pic.twitter.com/DXtWBjFTBq

— Antony Green – elections (@AntonyGreenElec) April 8, 2019

Delaying the election until May 25 would allow for more taxpayer-funded government advertising and avoid a pause in the campaign for the Easter long weekend.

However, the Clerk of the Senate, Richard Pye, has told The New Daily that it will be “a very tight time frame” if an election is not held until the last Saturday in May.

“If you want to bring the Parliament back on June 25, then by holding the election May 25 you are giving yourself exactly 30 days and that is a very tight time frame by historical standards,” he said.

The date that Parliament returns is critical, because tax cuts for 10 million Australians require the urgent passage of laws to ensure workers can secure the lump sum when they lodge their tax returns from July 1.

But the timing of the return depends on how quickly officials can count the vote.

The Australian Tax Office said on Monday it could not deliver the $1080 rebate proposed in the federal budget until laws are passed.

On Tuesday, advice from Mr Pye’s office to South Australian Senator Tim Storer warned a May 18 election would deliver a tight but feasible time frame to the new Parliament sitting in the final week of June.

“Unless the return of the writs is less than 30 days, following a May 25 polling date, it would be unlikely that the Parliament could be summoned in the last week of June,” the advice states.

According to Mr Pye’s office, the period between the election date and the return of writs (when successful candidates are declared) in the past four federal polls has been 28, 32 or 38 days.

Mr Pye said May 18 had been considered the last possible date for this year’s election because that was the information on the Australian Electoral Commission website. Overnight on Monday, that was removed.

“If the AEC is now saying a different date is possible, we will take their advice,” he said.

Senator Storer said a May 25 election raised real concerns about whether the government could deliver tax cuts promised in last week’s federal budget.

“Voters have the right to be concerned that the government cannot deliver on its pledge to put its promised tax cuts in workers’ pockets from July 1,” he said.

“It defies credibility for Scott Morrison to handcuff future parliaments when he cannot even guarantee his immediate tax cuts would be delivered on time.”

Last week, AEC commissioner Tom Rogers was asked to provide advice to Senate estimates hearings on the logistics of holding the election on May 11, 18 or 25.

“I am always nervous talking about dates so close to an event because I do not want to in any way presume what … the Governor-General or the Prime Minister may do,” he said.

“[But] the later we go, the more complex it becomes for the AEC. But that does not mean it is impossible.”

The AEC’s chief legal officer, Paul Pirani, said the Constitution allowed the House of Representatives to sit, even if the new Senate was not finalised.

“There is a provision in the Constitution that, should the Senate need to set at a particular time and should not all the senators have been returned, that technically the Senate would be still able to sit,” he said.