Boris Johnson stands accused of body-shaming a fellow MP in the Commons after he joked they had been "eating more cake" than him.
The SNP's Westminster leader, Ian Blackford, had launched an attack on the Prime Minister over Downing Street's lockdown-busting parties.
Urging Tory MPs to oust the PM, he said the cost of living crisis "hangs like a guillotine while they eat cake”.
It comes as Downing Street faces a police investigation over breaking lockdown rules and as the PM is braced for senior civil servant Sue Gray's report on the scandal.
Mr Blackford said: “Every moment that the Prime Minister lingers, every nick in this death by a thousand cuts is sucking attention from the real issues facing the public. Tory cuts, Brexit and the soaring cost of living have pushed millions of families into poverty.
“The impending National Insurance tax hike hangs like a guillotine while they eat cake. This is nothing short of a crisis and the only route out, the only route to restore public trust, is for the Prime Minister to go.
“How much longer will Tory MPs let this go on for? How much more damage are they willing to do? It is time to get this over with. Show the Prime Minister the door.”
The Prime Minister rather grumpily hit back, saying: “I don’t know … who has been eating more cake.”
He said: “Behind the scenes, people don’t get this, but actually we co-operate well and I want to continue to do so.”
Tom Quinn, director of external affairs for the eating disorder charity Beat, said: "'It is completely unacceptable that the Prime Minister should resort to making fatphobic comments.
"It shows a clear lack of regard for, or understanding of the 1.25 million people in the UK affected by eating disorders, and we are extremely disappointed that he has deemed this to be an appropriate response.
"We would urge the Prime Minister to educate himself on the seriousness of these mental illnesses, and limit his comments of other MPs to their actions, not their appearances."
The SNP's equalities spokesperson Kirsten Oswald, said: “ Boris Johnson has proven, yet again, that he is completely unfit for office.
"Whether it's his body shaming jokes, his racism, his homophobia, or his wider misconduct in public office, Mr Johnson is giving people another telling insight into his odious character.
"The Prime Minister's frequently offensive remarks will have a damaging impact on many young people and need to be called out. He is sending an appalling message to society, that the most powerful person in the UK government thinks it's ok to mock people because of their bodies, race, sexual orientation and religion.
"The longer Tory MPs allow Mr Johnson to cling onto power, the more damage they will do to any remaining public trust in this discredited government.”
