Lawyers for former Family First senator Bob Day have urged the High Court to reject evidence from two witnesses as the court considers whether he was validly elected.

The High Court has been asked by the Senate to consider whether Mr Day may have breached the constitution in the lease arrangements for his office.

The case is focused on who owned a building in Kent Town, South Australia, where Mr Day set up his electorate office.

The core of the case is the allegation that Mr Day, who has since resigned from the Senate, may have breached section 44 (v) of the constitution by having a direct or indirect pecuniary interest in the building which housed his electorate office.

Today, lawyers for former Labor senator Anne McEwen told the court Mr Day tried to hide the fact he had a financial interest in the building where his office was located.

Mr Day had owned the building which was sold to a company called Fullarton Investments, so he could meet his legal obligations as a senator.

Documents show Debra Smith as director: court

On Monday, Mr Day's former business partner John Smith, told the court Mr Day had asked for Mr Smith's wife to purchase the building.

Mr Smith said he only agreed on the condition it would not cost the couple anything.

He told the court Mr Day said he had taken care of everything.

Debra Smith who later became the sole director of Fullarton Investments, which bought the building, said she only signed documents and had no involvement in running the building.

Ms McEwan's lawyers told the court she was only ever a cipher and it was a paper arrangement.

But today Mr Day's counsel Andrew Bell told the court the long list of documents signed by Mrs Smith, which include minutes, show that was not the case.

"They show Ms Smith acting as a director, making decisions for Fullarton Investments giving effect to those directions," he told the court.

"She knew, fully understood she was a director of Fullarton Investments in this period."

Mr Bell said in one document she wrote the word 'Director' in her own handwriting.

Smith denies being director

Ms Smith denied knowing she was a director, and said she had no recollection of the document.

Mr Bell said the court should find she did understand what she was doing.

"She understood that she would acquire the property and that the property would be leased," he said.

"There's no evidence she executed any of those documents because she was told to or directed by Mr Day."

Ms Smith eventually withdrew from the arrangement, when her husband ended his 40-year partnership with Mr Day.

Mr Bell said there was also evidence of the new Fullarton Investments Director Colin Steiner was his own master, not taking directions from Mr Day.

Lawyers for the Commonwealth have also asked the court to reject calls by Ms McEwen's lawyers to omit votes for Mr Day in any recount.

Justice Michelle Gordon has reserved her decision on what issues the full bench of the High Court should consider.

It will be handed down in the coming days.

The full bench of the High Court will consider the case in February.