Ms Gray is looking into parties and gatherings in Downing Street following a series of scandals that has seen Boris Johnson’s authority evaporate.
Tory MPs are said to be waiting for the report before sending in letters of no-confidence, with the Prime Minister’s former chief adviser Dominic Cummings submitting evidence on Monday.
Speaking ahead of the report’s publication, Lib Dem MP Christine Jardine claimed the document must show “who was involved and exactly what the Prime Minister knew about these shenanigans”.
She continued: "Sue Gray's report must pull no punches in providing a full and transparent account of exactly what happened within Downing Street.
"But it also needs to be made absolutely clear that those within No. 10 are subject to the rules they make in exactly the same way as the rest of us. We cannot have it being one rule for them and another for everyone else.
"We also must see the report in full as there must be no cover-up, no interference from Boris Johnson, and no doubt that there are consequences for breaking the rules – whoever you are."
Labour’s shadow Scottish secretary Ian Murray demanded the report be published in full.
He said: “It is vital that the Government publishes the Sue Gray report in full, with all accompanying evidence.
"Reports that only a redacted or limited version will be published fly in the face of the principle of this report.
“The Prime Minister cannot try to hide or obscure his way through this crisis in leadership. All the evidence shows that has broken the rules and lost public trust.
“Even the Tories in Scotland can no longer pretend that he’s fit for the office of Prime Minister.”
SNP Westminster deputy leader Kirsten Oswald labelled the report a “distraction” and claimed the public already knew the Prime Minister had lied.
She said: “Boris Johnson has already admitted to breaking the law by holding and attending rule-breaking parties in Downing Street during lockdown.
"It’s also clear that he lied and misled Parliament by falsely claiming that there were no parties.
“Those are the established facts. The Sue Gray report is being used as a distraction. It might provide extra detail, but it cannot change the fundamental facts that the Prime Minister broke the rules and misled Parliament. He has already been caught red-handed.
“If Boris Johnson won’t do the honourable thing and resign, then Tory MPs have a duty to remove him from office.
"The longer they wait, the more damage they will do to any remaining public trust in the UK Government and Westminster system.”
It comes as Mr Cummings, who left Downing Street in November 2020, revealed his evidence was submitted in written form to Ms Gray rather than in person.
The former Vote Leave organiser explained "if we speak, the PM will invent nonsense and spin it to the media and you and I will both have problems".
Writing on his substack page, Mr Cummings added: “Therefore he [the PM] cannot invent things I've supposedly said to you. There is only a written record, this makes both our lives easier. She agreed.
"But I will not speak and therefore provide the PM with more chances to lie and confuse everybody."