An MP loyal to Boris Johnson shouted “wait and see” to protesters who turned out to watch his resignation, which some critics interpreted as a threat.
Andrea Jenkyns defied the jeering and booing crowd, as she and other MPs left Downing Street after supporting Mr Johnson as he delivered his resignation speech.
Raising a finger in the air for emphasis, Ms Jenkyns appeared to shout: “Those who laugh last, laugh loudest”, followed by “Wait and see”.
The Brexit-backing MP, who is a member of the European Scrutiny Committee, is an ultra-loyalist to the prime minister.
Mr Johnson said he was sorry that his arguments for staying on had failed to convince the party as he announced he would stand down after his successor had been agreed.
Boris Johnson resigns – live
He blamed “a herd instinct” for his ousting, and thanked his family, the civil service and the NHS, adding: “Above all I want to thank you, the British public for the immense privilege that you have given me. And I want you to know that from now on, until the new prime minister is in place, your interests will be served and the government of the country will be carried on.”
Soon afterwards, as she walked away from Downing Street, Ms Jenkyns also said the party would regret ditching Mr Johnson “like they did with Thatcher”, adding: “This will be a mistake.”
One Twitter user wrote: “‘Wait and see’ – are we heading for the UK’s own ‘January 6’ insurrection?”
On 6 January last year, supporters of Donald Trump, who refused to accept he had lost the US election, stormed the US Capitol. Five people were killed as the violent mob smashed through security barriers to go on the rampage inside.
Another wrote: “Sounds like a threat that Johnson isn’t finished.”
Many on social media made comments such as “Those who laugh last, didn’t get the joke.”