British Prime Minister Boris Johnson faces a large rebellion among his Conservative lawmakers on Tuesday in a parliamentary vote over new restrictions to try to curb the spread of the new Omicron coronavirus variant.

The measures, including ordering people to work from home, to wear masks in public places and use COVID-19 passes to enter some venues, are expected to be approved by parliament but with Johnson relying on the opposition Labour Party for votes.

It's yet another blow to a Prime Minister already under pressure over reported parties in his Downing Street office last year when such gatherings were banned, a pricey refurbishment of his apartment and the chaotic withdrawal from Afghanistan.

Many of his lawmakers say the restrictions are draconian, with several questioning the introduction of a certificate of vaccination or proof of a negative COVID-19 test to enter some venues, such as night clubs.

Others are using the votes as an opportunity to vent their anger at Johnson, believing the man who helped the Conservatives win a large majority at a 2019 election is squandering the party's successes by self-inflicted missteps and gaffes.

But despite the rumblings of discontent, Conservative Party insiders say there is not enough of a groundswell against Johnson to dislodge him yet, with no potential challenger commanding enough support to replace him.

"Boris on a bad day is better than any of the other wannabes on a good day," said one veteran Conservative, who spoke on condition of anonymity.

'HUGE SPIKE'

Before the series of votes on the measures, due to start at around 1830 GMT, Johnson warned his cabinet of top ministers that there was a "huge spike" in Omicron cases heading Britain's way, and that the measures were necessary to protect people.

"The PM said a huge spike of Omicron was coming and the measures we aim to introduce as part of plan B were balanced and proportionate, helping to reduce transmission while we ramp up the booster programme," his spokesman said.

Britain has registered almost 4,500 cases of Omicron, with 10 people hospitalised. One person has died after contracting the variant.

Ministers were acting to try to win over the Conservative rebels, noting that people who have not been double-jabbed can instead offer proof of a negative lateral flow test to gain access to indoor venues of more than 500 people.

Health minister Sajid Javid told lawmakers he firmly believed in "individual liberty" but that "the responsible decision to take is...to move to plan B in England".

Several remained unconvinced, with one, Andrew Bridgen, saying some lawmakers were determined to "draw a line in the sand with regard to any further erosion of civil liberties and freedoms".

Conservative former minister David Johnson described the move to introduce COVID passes as "quite wrong".

"People should certainly be encouraged to have the vaccine..., but ultimately people have to take responsibility for their own health," he told Reuters.