The Prime Minister must resign after being fined following an investigation into lockdown parties, and those who say now is not the right time for a change of leadership “couldn’t be more wrong”, a bereaved family member has said.

Rivka Gottlieb, who lost her father Michael to Covid aged 73 during the first lockdown in April 2020, said she feels “absolutely livid” and “disgusted” at the lack of honesty from those in charge of the country.

Boris Johnson “lost his moral authority a long time ago” and his position is “untenable”, the 50-year-old from north London said.

She told the PA news agency: “I feel like I’m watching a car crash in slow motion over and over again, and I’ve been saying this for months: the ineptitude and lack of integrity at the top has led us into this place.

“And I think that those who say now isn’t the time to change leadership couldn’t be more wrong.

“This is the leadership that got us into this mess. The situation in Ukraine is irrelevant to what’s happening internally in this country right now. And what we need is better leadership.”

Mr Johnson was fined for taking part in his own birthday bash in the Cabinet Room of No 10 in June 2020, Downing Street said on Tuesday.

Chancellor Rishi Sunak and the Prime Minister’s wife, Carrie Johnson, have both also been fined, but it has not been confirmed why.

Conservative MP Sir Roger Gale said now is not the time to “unseat” the Prime Minister, while Scottish Tory leader Douglas Ross has said it “wouldn’t be right” to remove Mr Johnson during the Russian invasion of Ukraine.

Ms Gottlieb said she is worried that the public would not listen to Mr Johnson if he remains in post and needs to introduce further coronavirus restrictions.

She said: “It is absolutely essential that the people in charge follow the rules, that they set the rules and they lead by example.

“So I fear very much that if there is a new variant or something else happens in the future, or a different pandemic, or whatever the situation is, people are not going to do what the Government tells them, because why should they if the Government doesn’t follow its own rules?

“It’s worrying, it’s deeply, deeply worrying.”

Ms Gottlieb is a member of the Covid-19 Bereaved Families for Justice group, which earlier called for Mr Johnson and Mr Sunak to step down after their “truly shameless” behaviour.

Bereaved families have said there is “simply no way” the Prime Minister and Chancellor can continue in their posts, and that they have lost all credibility with the public.

Lobby Akinnola, whose father Olufemi Akinnola died with coronavirus in April 2020 aged 60, said Mr Johnson and Mr Sunak would be “gone by tonight” if they had any decency.

He said: “There is simply no way either the Prime Minister or Chancellor can continue.

“Their dishonesty has caused untold hurt to the bereaved.”

The group said it is “now indisputable” that widespread rule-breaking occurred in and around Downing Street, after police  investigating allegations of lockdown parties made more than 50 referrals for fines.

The Metropolitan Police said at least 30 more fixed penalty notices will be issued by the ACRO Criminal Records Office, in addition to 20 referrals made at the end of March.

Matt Fowler, co-founder of the group, said it is indisputable that those in charge of the country were “partying and rule breaking en masse”, adding: “It’s a reality that is unbelievably painful for bereaved families like mine to face as we try and move forward with our lives.”