Desperate to stave off the chaos created by a divided party and doubts over Malcolm Turnbull’s parliamentary majority, the government has launched an extraordinary personal attack on Bill Shorten and created a diplomatic incident with New Zealand.

Overnight, the government opted to take the fight to Labor, claiming the opposition had colluded with a foreign political party and that Shorten was unfit to lead because of the Australian government’s amended industrial relations laws.

Accordingly, this morning Christopher Pyne accused Bill Shorten of colluding with New Zealand Labour to uncover Joyce’s New Zealand citizenship, thus undermining the Australian government. The Prime Minister later accused Shorten, in his address to the Coalition joint party room meeting, of trying to “steal” government. Assistant Treasurer Michael Sukkar went further and compared it to Cold War collaboration with the Soviet Union.

But Foreign Minister Julie Bishop went far beyond that in an extraordinary media conference in which she accused Shorten of undermining relations with New Zealand, and said she would not be able to trust the New Zealand government if Labor were elected — an astonishing intervention in New Zealand’s domestic affairs ahead of a general election there on September 23.

“Should there be a change of government, I would find it very hard to build trust with those involved in allegations designed to undermine the government of Australia,” she said.

But Bishop’s quarrel wasn’t merely with NZ Labour. The New Zealand government’s Internal Affairs minister Peter Dunne confirmed that its assessment of Joyce’s citizenship was in response to Australian media inquiries (from Fairfax journalists who have been pursuing the issue for over a week) rather than New Zealand Labour MPs. Bishop said that she refused to accept that.

The attack comes on top of continuing efforts to focus attention on Shorten’s history before he entered politics, with the government arguing that Shorten had in effect been corrupt when he led the Australian Workers’ Union and the union accepted payments from employers for training and membership deals. The government last week passed laws outlawing “improper payments” to unions and claimed Shorten might have been jailed if such laws were in place 15 years ago.

But the remarkable and cack-handed intervention of Australia’s Foreign Minister in New Zealand politics, in effect saying she would not work with the NZ government if Labour were elected in that country, represented a dramatic and escalation of rhetoric, and all for the political purpose of distracting from Barnaby Joyce’s astonishing blunder in not doing the most basic checks on his own background.