Shadow attorney-general Mark Dreyfus said it was misleading for the government to argue Barnaby Joyce and Fiona Nash could serve as ministers if they are ruled to be ineligible.

"That is not correct. The three months started from the date of their eligibility which is the date of their election to the parliament - and it ran out in October," Mr Dreyfus said.

Labor would not consider a full audit of the eligibility status of federal politicians until after the High Court dealt with current referred cases.

"If the High Court does what the government says it's going to do and radically rewrites the understanding of section 44 of the constitution then that's the time at which the situation of other members of parliament need to be considered," he said.

"Not before."

Labor is sharpening its attack against Deputy Prime Minister Barnaby Joyce after Bill Shorten finally quashed any doubts about his own eligibility.

After weeks of holding out, the opposition leader has produced proof he renounced his British citizenship prior to being elected in 2007.

Mr Shorten on Monday tabled a letter from UK authorities confirming his successful renunciation in June, 2006.

"I offer this proof to the parliament today to put an end to baseless allegations, not reward them," he said.

Labor continues to pile pressure on Malcolm Turnbull over a decision not to stand Mr Joyce aside, pending a High Court hearing over his eligibility.

A Labor suspension motion in parliament over the issue was headed off by a single vote.

Mr Shorten also wrote to the prime minister on Monday, saying if he failed to temporarily appoint a different acting leader it would put the legitimacy of the government into question.

He called for the release of the government's legal advice on Mr Joyce's eligibility.

Mr Turnbull said the government had very strong advice the High Court would find in favour of Mr Joyce, who discovered last month he was a dual New Zealand citizen because his father was born there.

Mr Joyce, who will be acting prime minister on Friday when Mr Turnbull heads to a summit in Samoa, said he would hold his job "until such time as death or you resign or the High Court finds otherwise".

The opposition leader's decision to table the letter came less than eight hours after former prime minister Tony Abbott challenged him to "show it or shut up" while brandishing his own proof of renunciation.

Mr Shorten told parliament Mr Abbott and Mr Turnbull had engaged in "conspiracy theories", and no MP or senator should be forced to produce documents to counter claims made without any evidence.