Senior coalition MP David Gillespie has received legal advice from a barrister that there is no constitutional problem with him sitting in parliament.
Dr Gillespie, the assistant health minister and Nationals member for the NSW seat of Lyne, owns a suburban shopping complex in Port Macquarie.
One of the shops in the complex is an outlet of Australia Post, a government-owned corporation.
Labor raised questions about the arrangement in the light of the High Court's disqualification of former Family First senator Bob Day over an electorate office leasing deal with the government.
Under Section 44 of the constitution anyone with a "direct or indirect pecuniary interest" in an agreement with the commonwealth is disqualified to sit as an MP.
Attorney-General George Brandis told a Senate committee on Tuesday he had encouraged Dr Gillespie to seek advice and that advice had been provided by experienced Sydney barrister Guy Reynolds.
"That advice is unequivocal that he doesn't have a problem," Senator Brandis said.
Senator Brandis said the "indirectness of the interest" went "nowhere near" the Section 44 prohibition.
He and the prime minister were satisfied with the advice, which had been paid for by Dr Gillespie.
However, asked by Labor senator Penny Wong whether the advice could be publicly released, Senator Brandis said it was a matter for Dr Gillespie.
