If Theresa May wins the general election on 8 June, many of her key cabinet ministers are likely to keep their jobs – just as May herself did when the Conservatives won in 2015. But the prime minister will also have every opportunity to move other members of the cabinet to jobs for which they are better suited. And among those ministers must surely be Elizabeth Truss, lord chancellor and secretary of state for justice.

Truss is a likeable, approachable politician, well able to hold her own with parliament and the press. She has a clear idea of her priorities and, after a slow start, has mastered her brief. But, when dealing with senior judges, she comes across as a lightweight.

At the beginning of last month, she told the House of Lords constitution committee that there was still a ‘myth’ about the so-called Kilmuir rules. ‘Those rules about judges not being able to speak out in public were abolished in the 1980s,’ she said, ‘and yet there is still sometimes a reticence to do so.’

I well remember the press conference in 1987 at which her predecessor Lord Mackay of Clashfern said that, in future, judges should decide for themselves how to deal with media requests. The judges remember it too. At the time, though, Truss was 12 years old. She would have no idea how much trouble Lord Woolf got into five years later when the then law lord appeared to criticise the ‘prison works’ policy espoused by Michael Howard, the home secretary. There are some occasions when reticence may be in the judges’ best interests, however much I try to persuade them otherwise.

But it was Truss who seemed reticent last November when the Daily Mail called the lord chief justice and two senior colleagues ‘enemies of the people’ for deciding that legislation was needed to trigger Brexit. By contrast, moments after that decision had been upheld by the Supreme Court she described its justices as ‘people of integrity and impartiality’. It was a tacit acknowledgment that she had got it wrong the first time round.

Asked subsequently to explain, Truss insisted that it was not her job to condemn the press. Indeed, it was not. But what she was being asked to do was to defend the independence of the judiciary, as she had sworn to do on her appointment. A more honest answer would have been to admit she had been poorly advised.

That was precisely the allegation made against Truss last month by the lord chief justice, Lord Thomas of Cwmgiedd. Three weeks after her own appearance, Thomas told the Lords constitution committee that an announcement by her officials about extending the use of pre-recorded evidence for vulnerable witnesses in criminal trials was simply wrong. ‘I regret to say that we had to correct a serious misapprehension that had arisen as a result of what the ministry said at the end of last week’, Thomas said. ‘They had misunderstood the thing completely.’

Again, Truss could have said she had been misinformed. Far from it: she made no attempt to correct the position, either when she spoke in parliament or by amending the misleading press release that remains accessible on the government website. A newspaper was apparently told, implausibly, that it had been ‘signed off by one of the most senior judges’.

In his evidence to the committee, Thomas laid into Truss over her remarks about judicial reticence: ‘The idea that we do not realise that the Kilmuir rules have gone is quite frankly fanciful.’ What Truss had not understood, he implied, was that no serving judge could have responded to the Daily Mail at that time without plunging the judiciary into political controversy. And some readers believed what they read. ‘The circuit judges were very concerned,’ he said, ‘because litigants in person were coming and saying, “You’re an enemy of the people”.’

Asked about Truss’s insistence that it was not her job to censor or direct the press, Thomas said she was under a duty to defend the judiciary from unwarranted attacks. ‘I regret to have to criticise her as severely as I have, but to my mind she is completely and absolutely wrong about this,’ Thomas said. ‘It really is absolutely essential that we have a lord chancellor who understands her constitutional duty.’

It is hard to see how Truss can survive measured and devastating criticism like this from the most senior judge in England and Wales. Thomas will have more to say about her in a lecture he is to deliver in parliament on 15 June. But by then, if the prime minister is attuned to the views of those with whom the lord chancellor must maintain a close working relationship, Truss may no longer be custodian of the great seal.