Some 20,000 Brits have demanded changes to plans for the Covid-19 public inquiry.
It comes after campaigners were left furious over the draft list of what will and will not be considered by the probe.
Partygate and the impact of the pandemic on mental health and people with disabilities were not mentioned in the proposed list of subjects, published last month.
And Boris Johnson will get the final say on what topics the inquiry will cover.
Writing for the Sunday Mirror, Labour leader Keir Starmer said: “Boris Johnson is the first sitting Prime Minister to have broken the law. But he is brazenly clinging to the office he has so shamelessly abused.
“Taking his disrespect for the public to new depths. It’s no wonder 20,000 Brits want answers.”
Care Campaign for the Vulnerable - one of the first organisations to call for a public inquiry on the handling of care homes during the pandemic - criticised the absence of partygate.
Founder and Director Jayne Connery said: "We saw first hand when supporting families the torment suffered when told they could not visit elderly loved ones in care homes - and two years on families are now officially diagnosed with mental health issues including PTSD.
"The partygate fiasco only adds to the pain and heartache felt by families when the government failed to understand the impact their “guidance“ on care homes during the pandemic had on our most vulnerable elderly.
"The PM choosing what can and can’t be examined at the forthcoming public inquiry is certainly not what we would wish for - especially after the PM and his supporters were not transparent regarding their own rule breaking."
Lobby Akinnola lost his 60-year-old father Olufemi “Femi' Akinnola, a Mencap support worker, to Covid-19 in April 2020.
The 30-year-old, a member of Covid-19 Bereaved Families for Justice, said: "It's not surprising when people across the country, after sacrificing so much during the pandemic, want the partygate scandal investigated and included in the Covid inquiry's scope.
"We have already called for the inquiry to cover any and all public health messaging and actions which undermined those messages and it is hard to think that breaches of the law by Government ministers and officials would not impact this and could have cost lives."
Under the Prime Minister’s proposed plan, the probe would investigate how prepared the UK was for a pandemic, public health responses, how the Health service and care sector coped and the Government’s economic response.
The inquiry, chaired by crossbench peer Baroness Hallett, invited the public to comment on the proposed ‘terms of reference’ - and tens of thousands responded within just four weeks.
Inquiry officials are busy analysing the responses, and will publish their recommendations for changing the terms of reference next month.
Announcing the closure of the consultation last week, Baroness Hallett said: “I hope to make my final recommendations on the UK Covid-19 Inquiry’s Terms of Reference to the Prime Minister in May. He will then make his final decision on the Terms of Reference. Once I have his decision, the Inquiry will begin its work formally.
“In the meantime, my team and I are working hard to analyse the many issues that the Inquiry will have to cover and produce a plan of the way we intend to work and gather evidence.”
