Corbyn was pictured alongside seven other guests at a dinner in London that took place last Saturday – less than two weeks after rules on social gatherings of more than six people were banned.
In total, nine people were at the party, according to The Sun – meaning each person could be fined under the new rules.
Now Labour’s shadow minister for mental health, Rosena Allin-Khan, has said that Corbyn “rightly should be paying the fine”.
Speaking to Sky News, Allin-Khan said she was “disappointed” in her former leader, who has since apologised for flouting the regulations.
She said: “I'm glad Jeremy Corbyn has apologised. It is absolutely inexcusable for people to break the rules.
“The rules apply to everyone. He rightly should be paying the fine.”
Corbyn admitted to The Sun that “remaining at the dinner was a breach of the rule of six” adding: “I apologise for my mistake.”
However, environment secretary George Eustice insisted that Corbyn should not have to pay the fine as it appeared to be a one off.
Watch: Rule of six explained
He told LBC: "My view is fines should be reserved for people who are wilfully and repeatedly breaching one of the regulations we put in place."
Eustice added to Sky News: “We have the rule of six, and it’s being enforced and should be enforced, yes.
“But that doesn’t mean that there should be a penalty in every case.
“Sometimes it can be a warning, sometimes people make mistakes and apologise for it.”
But David Morris, Tory MP for Morecambe and Lunesdale, told The Sun: “It is beyond belief that an MP – and someone who claims to stand up for the common man – has behaved this way.”
Corbyn’s rule breach comes as the prime minister’s father was also caught breaking coronavirus guidelines after he was pictured in The Mirror walking around a shop without a face mask.
Stanley Johnson, 80, said he was “extremely sorry for the slip up”, adding: "The fact this was my first day back in the UK after three weeks abroad is, I am sure, no excuse for not knowing the rules.”
Boris Johnson also apologised this week after he came under fire for not knowing the detail of new lockdown measures for north-east England, which came into force on Wednesday.
Johnson apologised after the gaffe and swiftly issued a correction with details about the restrictions.
Earlier this year reports suggested Johnson’s senior aide Dominic Cummings allegedly broke the government’s lockdown rules when he was spotted at his parents’ property in Durham where he was recovering from coronavirus symptoms, after travelling from his London home with his wife and son who also fell ill.
Cummings defended his actions in a press conference in the Downing Street rose garden, saying he believed he behaved “reasonably” and did not regret his actions.
Watch: £10,000 fines for refusing to self-isolate