Federal government MPs are making contingency plans in case the May budget is brought forward by a week as the Prime Minister considers a July double-dissolution election over blocked anti-union corruption bills.

While officially at least, the government maintains it is working in the normal way towards a May 10 budget, Fairfax Media has been told a series of alternative logistical arrangements are being put in place for a late switch to May 3, among which is the reservation of Parliament House's Great Hall.

An inquiry to Parliament House regarding the hall's availability that night confirmed it had been "reserved" although it did not reveal the identity of the person making that reservation.

The salubrious 600-seat venue is normally used by the governing party on budget night to conduct its largest, most lucrative fundraising activities with, what one insider described as $1000-a-plate meals ranging right up to several thousand dollars for tables hosted by ministers and perhaps twice that for those graced with treasurer and prime minister of the day.