William Hague, who led the Conservative Party in opposition from 1997 to 2001, said that Mr Johnson had done things that made defending him “very hard” and that the “inconsistency” of his public utterances and private behaviour were making things difficult. Lord Hague and Mr Johnson have found themselves in opposing political camps in recent years.
The ex-Foreign Secretary, an ally to David Cameron, campaigned for the UK to stay in the European Union while the then Mayor of London backed Vote Leave.
Lord Hague subsequently endorsed former Health Secretary Jeremy Hunt as Tory leader when Mr Johnson emerged victorious in the race to succeed Theresa May in 2019.
But Lord Hague, an MP from the Thatcher to Cameron era, started by arguing that defending leaders was an integral part of party politics.
Writing in the Times, he said: “When Margaret Thatcher was reviled, I was a schoolboy activist sticking up for her in the Yorkshire coalfields.
“When John Major’s leadership was under threat, I helped run his re-election campaign.
“Many of these leaders also defended me when I was party leader, and I really needed defending.
Speaking about the Prime Minister, Lord Hague added: “So, in Boris Johnson’s case, even though I didn’t approve of Brexit, preferred Jeremy Hunt in the leadership election and have often disapproved of how the Government has been run, I have still tried to speak up for him.
“Much of what Johnson does is easy to defend. His conduct of British policy on Russia’s war in Ukraine has been excellent, and that matters as much as anything in the world at present.
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“The inconsistency of manner and approach tends to undermine his support rather than secure it.”
Mr Hague went on to claim Mr Johnson’s leadership may be in trouble due to discipline among Tory MPs, the decision by MPs to allow the Privilege Committee to investigate whether the Prime Minister misled the Commons over partygate and loyal Brexiteers withdrawing support for Mr Johnson.
He said: “One was the failure of the whips to anticipate that tabling a motion to delay the whole issue risked resignations and defeat.
“This is not because they are poor whips, but because MPs have stopped volunteering how uncomfortable they are: the prelude to previous leaders being deposed, such as Heath in 1975 and Thatcher in 1990.
“Second, the Privileges Committee will eventually — once the Met has concluded its investigations — do its weighty work.
“Since being found knowingly to have misled parliament without correction is an unquestionably capital offence for any minister, the day will come when the PM’s future might hang by the thread of one vote by one MP.
“And the third ominous sign was the utterances of Steve Baker, the MP for Wycombe.
“On Tuesday he extended his forgiveness to Boris Johnson, yet by Thursday he had withdrawn it.”
According to the Times, Sue Gray’s partygate report may be so damming that Mr Johnson may have to resign as Prime Minister.
It is thought Ms Gray’s report will be highly critical of Mr Johnson not just in terms of his behaviour in relation to the lockdown breaking parties but also the culture within Downing Street.
The report has been put on hold for now while Scotland Yard completes its own investigation, dubbed ‘Operation Hillman’.
According to ITV, as many as 46 Tory MPs have now submitted letters of no confidence to the Chairman of the 1922 Committee Sir Graham Brady.
If true this would mean that only 8 more MPs need to submit letters of no confidence to force a ballot on Mr Johnson’s leadership to take place.