Malcolm Turnbull’s decision to stymie Kevin Rudd’s bid to run for the United Nations secretary-general post is ill-judged, unjustified and unfair.

It is a capitulation to the Liberal conservatives. It humiliates Foreign Minister Julie Bishop, who argued strongly that Australia should nominate Rudd. It denies a former prime minister a right that he should be accorded.

It will make Australia look wacky in the eyes of many in the international community.

Turnbull refused a last-minute request by Rudd, made Thursday evening, for a face-to-face meeting in Sydney on Friday morning. One would have thought it would be courteous to see him, even if it were to convey the bad news personally.

Turnbull told a news conference his judgement was that Rudd is “not well-suited for this particular role”. He declined to spell out why, though declaring it had nothing to do with Rudd being Labor.

To say a former prime minister and a former foreign minister, who is well-regarded internationally, is unsuitable for unspecified reasons is character assassination by silence.

Surely this is unacceptable. Most decisions are expected to be justified by reasons. Why not this one? Turnbull can hardly say it is to save Rudd’s feelings when he has cut him off at the knees and embarrassed him on the international stage. It’s as if Turnbull is implying we all know about Kevin so there is no need to explain anything.

Rudd’s Liberal critics argue he has a maniacal leadership style and would run wild on the international stage. Some at the heart of government, buttressed by the opinion of sources in officialdom, have persuaded themselves he would cause such problems that permanent Security Council members would be on the phone to the Australian government, saying: save us from Kevin.

It is important to understand just what was being sought. Rudd needed nomination to stand. As Bishop argued to colleagues, nomination did not amount to endorsement – although this was a distinction Turnbull rejected, believing nominating Rudd implied support for him.

Those around Turnbull insist he really believes refusing Rudd is the right thing to do. Maybe, but what is also obvious in this decision is that Turnbull’s authority in the party is tenuous and he cannot safely afford to defy the right-wingers, certainly on a non-core issue. They had him just where they wanted him.

Otherwise, even if he had some personal doubts, he would surely have gone along with the very strong representations of his foreign minister, who argued the precedent of supporting Australians going for international jobs, as did the Hawke government when Malcolm Fraser (unsuccessfully) pitched to become secretary-general of the Commonwealth.

Key interventions in this battle have been those of Treasurer Scott Morrison and Immigration Minister Peter Dutton.

Both Morrison and Dutton are tribal – no doubt they genuinely believe Rudd should not be facilitated in anything he wants to do. But there are some other factors at play as well, shown by the willingness of both to go public with their opposition before the cabinet meeting.

Morrison, who is commendably battling conservative critics over superannuation, has an eye to showing he is still one of them. Dutton would be pleased to see the popular Bishop take a tumble. In the longer run he has an eye on her position of deputy leader.

Rudd put his application to the government in April. In May Turnbull spoke to him, warning it would be difficult to get it through cabinet. Bishop is said to have been more encouraging, suggesting things might be easier after the election.

Possibly, if Turnbull had had a really good win, they might have been.