Bob Day may have illegally voted in the Senate for more than two years

AN explosive legal problem could put at risk legislation - including the same-sex marriage plebiscite - for the rest of the year.

Crossbench Senator Bob Day speaking to the media.

PARLIAMENT is in turmoil because financially-troubled Bob Day might have illegally voted in the Senate for more than two years.

The explosive legal problem could put at risk Government legislation - including the same-sex marriage plebiscite - for the remainder of the year.

As well, it casts a shadow over every Senate vote since July 2014, when South Australian Mr Day entered Parliament and established a record of backing the Government in roughly 95 per cent of ballots.

And it is expected to re-heat the row between Attorney-General George Brandis and departed Solicitor-General Justin Gleeson, who had concerns about the Senate’s composition.

The High Court has been called in to resolve the issue, but the Upper House will almost certainly have 75 and not 76 members for the remaining three sitting weeks. That means 10 instead of 11 crossbench members.

The central problem is a section of the Constitution which says an election candidate cannot have a pecuniary interest from the Commonwealth.

It seems Mr Day, from Family First, had his electorate office in a building owned by a company to which he had links. He was not only taking a salary from taxpayers, he was collecting rent from them.

Mr Day resigned from the Senate today in a surprise move.

He had previously said he would stay in Parliament until the end of the year to support the Government on key legislation. Then he would resign to help repay people owed by the collapsed home building group he had links to.

But it now appears he had to change his mind as he knew last Friday at the latest he should have been disqualified from standing for election.

“Last Friday, the Special Minister of State (Scott Ryan) wrote to the President of the Senate, Senator Stephen Parry providing certain information concerning the position of Senator Bob Day,” said a statement today by Senator Ryan and Senator Brandis.

“He also wrote to Senator Day regarding this matter.”

The Parliament’s big problem is what to do next.

One option would be to recount every South Australian Senate vote from the July 2 election and find a replacement for Mr Day right way.

That’s what Labor’s Senate Leader Penny Wong canvassed.

“If he was not (legally elected), Mr Day’s resignation would not create a casual vacancy because he was never validly elected in the first place,” said Senator Wong.

“Precedent suggests the appropriate method for replacing Mr Day in the Senate would therefore be through a recount of the SA Senate vote rather than through the SA Parliament appointing a replacement.”

There will be a big legal debate in coming weeks, and not just in the High Court.

“Labor will take independent legal advice on the complex issues involved in this situation, including whether it is desirable to refer the matter to the Court of Disputed Returns,” said Senator Wong.

“We will take a principled approach by seeking to ensure that the situation is resolved in accordance with the Constitution and electoral laws, that the outcome reflects the democratic will of SA voters and that the matter is dealt with transparently and openly.”