Veteran Conservative MPs have urged colleagues to endorse the privileges committee report on Boris Johnson in the House of Commons on Monday, as jittery Tories consider skipping an expected vote.

The committee condemned the former UK prime minister for contempt of parliament, including lying to MPs over the Covid-19 partygate scandal, in a damning 108-page report published on Thursday.

A 90-day suspension from the Commons would have been recommended if Johnson had not already quit as an MP, the report said. Instead, it has recommended he is blocked from receiving a pass to access the Commons, which is ordinarily extended to all former MPs.

The report will be debated in parliament on Monday and is expected to be put to a vote.

A clutch of Johnson’s allies including Sir Jake Berry, Sir Simon Clarke and Brendan Clarke-Smith have declared their intention to vote against the report, although they admit they do not have the numbers to win.

Some loyalists have warned colleagues who back the report that they could face battles with their local parties to remain as candidates at the general election. Nadine Dorries said that “any Tory MP who endorses this report does not respect democracy and must face deselection”.

In the wake of such threats, and fearful of upsetting local members who champion Johnson, a series of Tories privately admit they plan to be absent from parliament on the day in order to miss the vote.

The Tory whips have decreed that attendance in the Commons on Monday is not compulsory, giving MPs the option to miss it. Downing Street is yet to indicate whether Prime Minister Rishi Sunak will vote.

On Friday, however, ex-cabinet minister Damian Green urged fellow Tory MPs to turn up, telling the BBC the report was “very clear-cut” and that “parliament should respect its own procedures”.

Green said: “Deliberately abstaining is not really rising to the importance of the occasion.” It “particularly falls on backbenchers to care about the future of parliamentary discipline”, he added.

John Baron, a veteran Conservative who has been an MP for more than 20 years, also stressed the importance of defending the privileges committee’s inquiry into Johnson.

“We must maintain the integrity of the House, of parliament, we must endorse that report if it comes to a vote.”

Johnson loyalist Sir Jacob Rees-Mogg signalled the government was prudent to allow a free vote on the matter, warning a whipping operation would be unlikely to be successful given the strength of feeling among backers of the former PM.

Grassroots party members who support him are being urged to lobby Tory MPs ahead of the vote and make clear their concerns about Johnson’s treatment.

The Conservative Democratic Organisation, a group launched by Johnson’s allies after his departure from Downing Street, has been inundated with messages from activists who are furious about the privileges committee report, according to its chair David Campbell Bannerman.

The former Tory MEP said swaths of party members were “concerned about what they call a stitch-up, what I call a coup”. In a warning to Conservatives in the Commons, he said the CDO was advising members on the process of deselecting their local MP.

As splits in the party were laid bare, Sunak faced another blow as Telford MP Lucy Allan announced she would step down at the next election.

She said of the Shropshire town where Johnson launched his 2019 manifesto: “Today’s Conservative party is just not interested in seats like Telford anymore.”