Jeremy Corbyn is under pressure to sack any colleagues who refuse to vote against the EU Withdrawal Bill on Monday, or see his anti-hard Brexit stance “exposed as a sham”.

The Labour leader must “show the same ruthlessness” he displayed when sacking frontbenchers who defied his orders by trying to keep the UK in the single market, the Liberal Democrats said.

The demand comes after about 30 Labour MPs met Keir Starmer, the Shadow Brexit Secretary, to express their reluctance to oppose the withdrawal bill, as Mr Corbyn has instructed.

There were “heated discussions” as MPs from Leave-backing areas warned they would be tarred as trying to obstruct Brexit itself, The Independent was told.

Brexit: the deciders Show all 8 1 /8 Brexit: the deciders Brexit: the deciders European Union's chief Brexit negotiator, Michel Barnier Getty Brexit: the deciders French President Emmanuel Macron Getty Brexit: the deciders German Chancellor Angela Merkel Reuters Brexit: the deciders Commission President Jean-Claude Juncker EPA Brexit: the deciders The European Parliament's chief Brexit negotiator Guy Verhofstadt Getty Brexit: the deciders Britain's Prime Minister Theresa May Getty Images Brexit: the deciders Britain's Chancellor of the Exchequer, Philip Hammond PA Brexit: the deciders After the first and second appointed Brexit secretaries resigned (David Davis and Dominic Raab respectively), Stephen Barclay is currently heading up the position PA

Some are expected to break a three-line whip by abstaining – on a key night in the Brexit drama, when Labour hopes some Conservatives will also stage a rebellion.

Mr Corbyn has been persuaded to vote against the bill on the grounds it is a Government “power grab” that will allow future laws to be made using “Henry VIII powers”, but some in Labour fear the move will backfire by making the party look “anti-Brexit”.

Tom Brake, the Lib Dem Brexit spokesman, pointed out three Labour shadow ministers were sacked in June after backing an amendment to the Queen’s Speech in favour of staying in the single market.

In February, Clive Lewis was among frontbenchers forced to leave Mr Corbyn's team after refusing to back the legislation to trigger Article 50 and start the exit process.

“The chance to inflict a historic defeat against the Government's hard Brexit plans rests on whether Jeremy Corbyn can show leadership and keep his party united,” Mr Brake said.

“Corbyn must show the same ruthlessness towards his pro-Brexit MPs as he has to pro-European ones in the past.

“Any frontbenchers who defy the party whip should be sacked, or else Labour's recent shift towards supporting a softer Brexit will be exposed as a sham.”

Theresa May is in little danger of losing the most crucial vote on the second reading of the withdrawal bill, with only pro-EU veteran Ken Clarke threatening to vote against it.

However, an earlier vote on what is called the “programme motion” for the legislation could be closer, after criticism that the Prime Minister is refusing to allow sufficient detailed debate.

Only eight days have been set aside for line-by-line examination in committee, far fewer than when Britain joined the EU in the 1970s (22) or for the Maastricht legislation in the 1990s (23).

Yet the bill must carry out the daunting task of pasting 40 years of EU law onto the UK statute book ahead of Brexit day in 2019, before ministers propose which parts should be repealed.

It will be at that later stage that amendments – on anything from single market membership, to guaranteeing workers’ rights and environmental protections – will be tabled.

Pro-EU Tories are pressing privately for more days in committee before deciding whether to back the programme motion in Monday’s first vote, to take place no earlier than midnight.

One minister told The Independent: “If we lose the programme motion it will be a nightmare, because we would then be unable to shut down debate on any evening. MPs could force us to sit all night.”

A handful of Leave-supporting Labour MPs will support the second reading. One, Kate Hoey, warned that opposing it amounted to “betraying the will of the British people”.