The Federal Opposition and the Greens have ramped up their criticism of Family First Senator Bob Day, who seems to be hedging his bets on whether to resign from the Senate amid hopes of a financial bailout.

Last week Senator Day signalled his intention to resign as a senator for South Australia as his construction business went into liquidation.

Home Australia Group, once a financial success story, collapsed with more than 200 homes in five states still under construction.

But on Friday Senator Day confirmed he may retain his seat in the Upper House as an investor circled the business, allowing him to remain in Parliament and vote on key pieces of legislation such as the reintroduction of the construction watchdog, the Australian Building and Construction Commission (ABCC).

The backflip has drawn the ire of Opposition Leader Bill Shorten.

“Although Bob Day himself has declared his position untenable, has left a trail of unpaid subcontractors and distressed families without completed homes behind him, the Liberals are willing to keep him in the Senate for just long enough to secure one more vote in their attack on unions,” Mr Shorten told the Queensland ALP state conference on the Gold Coast.

“This is a morally weak Prime Minister, a morally bankrupt Prime Minister relying upon an insolvent senator.”

Senator Day has been an outspoken supporter of the ABCC legislation, and was even relied on by the Government to help secure the support of crossbench senators in the last parliament.

Greens Leader Richard Di Natale again called on Senator Day to resign immediately, and devote his efforts to supporting the families hit by the collapse of Home Australia Group.

“Your responsibility now is to look after them, not to play silly politics, not to be in cahoots with the Government to pass legislation,” Senator Di Natale told reporters in Melbourne.

Day’s future in his hands: Government

The Government maintains it is Senator Day’s responsibility to decide on his fate, and it will not get involved in his financial affairs.

Under the constitution, an individual cannot serve in parliament if they are bankrupt or insolvent — a position Senator Day has not yet reached.

While he is in the Senate, his vote will count.

Cabinet Minister Steve Ciobo said it was “not a case of accepting Bob Day’s vote or not”.

“The simple fact is that Bob Day is a senator, he’s not a member of the Government, he makes decisions about where he casts his vote,” he said.

Mr Ciobo argued the Labor party was in no position to lecture the Coalition on accepting “tainted votes”, saying the party had stood by disgraced former ALP member Craig Thompson.

Fellow South Australian Nick Xenophon wished Senator Day luck in finding an investor to salvage the business.

“I’m sure there’ll be some in the Senate that will say his vote is tainted, it won’t be me, but I think he can expect to be in for a pretty fiery time,” Senator Xenophon said.

One Nation Leader Pauline Hanson and Liberal Democrat Senator David Leyonhjelm have previously indicated Senator Day’s tenure in the Senate is a decision only he can make.