Politicians can make very good ambassadors. But when too many former politicians are on the diplomatic circuit, there is a cost to good diplomacy – a problem that Australia must now confront.

It’s true both Coalition and Labor governments have a long history of dispatching former ministers or MPs to represent the nation overseas. But a record has been achieved during the Abbott-Turnbull-Morrison years. In the Abbott era in particular, the ratio of political appointments versus career diplomats in top diplomatic jobs was the highest in Australia’s modern history, at one stage roughly one-in-ten.

More are being announced. Foreign Minister Marise Payne at the weekend made former NSW Liberal Patricia Forsythe Australia’s representative in Wellington. A few weeks back, Liberal ex-senator David Bushby was winging his way to be consul-general in Chicago. They join the ranks of former attorney-general George Brandis, camped in London as High Commissioner, and former treasurer Joe Hockey, Australia’s man in Washington. There are others besides, names less recognisable of former political staff sent to represent Australia abroad.

But what has changed in recent years is the apparent unravelling of an old political truce: once sent overseas, these former politicians were allowed to serve their term regardless of a change of government back home. This began with the Coalition, who on coming to government in 2013 torched plans to send the former Victorian Labor premier Steve Bracks to a consul role in New York. In Labor ranks, this was seen as an act of petty partisanship, compounded when former Liberal senator Nick Minchin snared the job instead.

Now it appears payback is on the way. A report on Monday claimed up to six former Coalition MPs appointed high commissioners, ambassadors, or consuls could face the chop should Labor win the next election, with foreign affairs spokeswoman Penny Wong saying Labor would “certainly be looking at” recent diplomatic appointments.

What has changed in recent years is the apparent unravelling of an old political truce: once sent overseas, these former politicians were allowed to serve their term regardless of a change of government back home.

These postings of politicians abroad are almost always described in the media as “plum”, the unsubtle code being that the position is a cosy retirement gig on the taxpayer’s purse. And undoubtedly, at the time it might be that the offer of a diplomatic post is a good way to coax a stale backbencher out of parliament or reward a minister dudded in a reshuffle.

But there can also be a benefit. Diplomats often have foreign language skills. But in a heady political town such as Washington, for instance, it can help to have a representative who speaks “politician” ­– someone who intimately understands the pressures of running for election, who can better engage with fellow politicos to build strong relationships, but also has (perhaps just as importantly, be seen to have) longstanding ties right the way to the top back home. In a diplomatic relationship, the other side wants to know its messages are being heard. If Joe Hockey picks up the phone, for instance, Scott Morrison will answer.

But this is where the problem Australia now confronts starts to become clear. Relationships – whether foreign or domestic ­– are predicated on trust. If Bill Shorten sits in the Prime Minister’s Office rather than Morrison after the next election, will the Labor leader listen to Hockey’s advice?

This is a problem Australia has actually encountered before. After defeating Kevin Rudd in 2013, Tony Abbott inherited former Labor leader Kim Beazley as ambassador in Washington. The Coalition made a deliberate choice to extend Beazley’s term, to signal to Barack Obama’s team in the White House that Beazley still had the ear of Canberra. (Some in Labor gave no credit, seeing the move as a cover for sacking Steve Bracks).

Likewise, in 2007, Kevin Rudd was under pressure from within Labor to recall then newly appointed ambassador to Italy and former Liberal senator Amanda Vanstone, but in keeping with past practice, allowed her term to serve out.

Yet Rudd won no favours. In 2016 came the spoiler role by Malcolm Turnbull in refusing to back Kevin Rudd’s bid to be UN chief. Rudd was a polarising figure, but as prime minister, he had supported former rival Alexander Downer to a UN special envoy role in the Cyprus conflict and made a point (to some annoyance within Labor) of sending former Coalition MPs abroad, such as Tim Fischer to the Vatican and Brendan Nelson to Brussels.

If tribal politics has indeed wound its way into the view of ex-politicians in diplomatic jobs, this will be disruptive to Australian diplomacy – just in the same way the long absence of an American ambassador in Canberra is interpreted by some as a snub. In the US system, there is a tradition that politically appointed ambassadors resign their post after a presidential election. Yet since Donald Trump’s victory in 2016, it has taken almost two-and-a-half years later to see a replacement board a plane.

Australia could adopt a similar practice of having former politicians turned diplomats quit after a change of government back home to save ugly displays of partisanship. But then Australia would also suffer the gaps as a new government finds its feet. Given the rate of appointments, rather than mass resignation, a better way might be to borrow from the style of American congressional hearings before confirming an ambassador in the post.

This would be essentially a competency test, and if held by a parliamentary committee, it would allow both Coalition and Labor members to quiz a would-be top diplomatic envoy about to be sent to represent the country. A former senior cabinet minister or experienced politician would have nothing to fear from robust questioning – and it would allow both sides of politics some ownership of the appointment, building trust.

Could these hearings become politicised, with delays and filibustering? Potentially. But it would also be a shame to surrender parliament only to partisan games rather than see it as a venue to strengthen the administration of policy.

Australia should adopt confirmation-style hearings not just for former politicians but all head of mission positions. Some of these hearings will be fairly brisk – Vientiane is unlikely to be controversial ­– but open hearings would escape the opaque manner in which these jobs are given, and assess other appropriate candidates who might be drawn from areas of government outside the Foreign Affairs portfolio, or from the business community, or state government.

The cunning old saying is that an “ambassador is an honest gentleman sent to lie abroad for the good of his country”. Seeing the right man or woman in the job, capitalising on their experience, connections, and knowledge should be the test for Australian diplomacy.