Former chancellor Sajid Javid is among a growing number of Tory MPs expected to rebel or abstain at a vote on Boris Johnson’s controversial Internal Market Bill.

Two former barristers – the ex-attorney general, Geoffrey Cox, and Rehman Chishti, who quit as the special envoy on religious freedom – have also told the government they will not back the bill tonight.

The possibility that rebels could lose the Conservative whip has not been ruled out.

Javid, who resigned from the cabinet earlier this year, said it was not clear why it was necessary to break international law.

He said instead the UK should wait until it was clear the EU intended to act in bad faith and until then use the safeguards already enshrined in the withdrawal agreement.

Meanwhile Geoffrey Cox, Mr Johnson's former attorney general when the Withdrawal Agreement was signed, told Times Radio that the Government "knew" what it was signing up to when it ratified the exit terms.

"What I can say from my perspective is we simply cannot approve or endorse a situation in which we go back on our word, given solemnly not only by the British Government and on behalf of the British Crown, but also by Parliament when we ratified this in February, unless there are extreme circumstances which arrive involving a breach of duty of the good faith by the EU," he said.

The Brexiteer warned he would not back the UK Internal Market Bill unless ministers dispel the impression that they plan to "permanently and unilaterally" rewrite an international agreement.

Mr Chishti tweeted: "As an MP for 10 years and former barrister, values of respecting rule of law and honouring one's word are dear to me."

Simon Hoare, Tory chairman of the Commons Northern Ireland Affairs Committee, said Mr Cox's condemnation of the Government's plans could not be ignored.

Tory chairman of the Justice Select Committee Sir Bob Neill said he cannot vote in favour of the UK Internal Market Bill at second reading unless clauses giving ministers powers to modify or disapply rules relating to the movement of goods between Britain and Northern Ireland are removed.

Sir Bob told the Commons: "I see the Chancellor of the Duchy of Lancaster (Michael Gove) listening, I hope he'll be able to go further than the Prime Minister either tonight, or in the course of this Bill, and assure us that those provisions will not be brought into effect unless and until every one of those legal mechanisms open to us have been exhausted and unless and until there has been a specific vote of this House."

He added: "I hope that we will take the opportunity to change and improve these clauses and the way in which they might operate so that we do not fall into a means of damaging our reputation.

"That is why I can't support the Bill tonight, I hope that we will see amendments to change what I believe are egregious and needless and potentially damaging elements of part five of the Bill."

Fellow Conservative former ministers Jeremy Wright and Andrew Mitchell also told the Government that supporting these measures would weaken the UK's authority on the global stage.

Fellow Conservative Imran Ahmad Khan (Wakefield) became the first of the new 2019 intake of MPs from the Government's own party to announce he will not vote for the Bill.

"Whilst I stand four-square behind the Government's policies and objectives, including those advanced by the UK Internal Market Bill, I cannot vote for legislation that a Cabinet minister stated from the despatch box will break international law," he told MPs.

Tory former attorney general Mr Wright agreed, adding: "If we break (international laws) ourselves we weaken our authority to make the arguments the world's most vulnerable need us to make."

Meanwhile, Conservative Mr Mitchell warned the Government that whilst he has "no hesitation in supporting the second reading" of the UK Internal Market Bill, he will vote against anything that breaches international law.

Mr Mitchell said: "Now I've voted in ways in this House that I have regretted in the past. I voted for Section 28, I voted for the poll tax and I voted with the then prime minister on Iraq.

"But I don't believe I've ever gone into a lobby to vote in a way that I knew was wrong and I won't be doing it on this occasion either."

Another Tory former minister, Sir Oliver Heald, expressed his unhappiness at the Government claiming precedent for breaking international law.

Sir Oliver said: "Can I just also say that I was surprised to see this justified by the precedent, allegedly, of the Finance Act 2013 General Anti-Abuse Rule by the Secretary of State for Northern Ireland.

"I was a law officer at the time, Dominic Grieve was attorney general. And one thing I can say about Dominic Grieve is that he was very correct and made sure that Government legislation did not offend the rule of law - he was extremely painstaking. And that Act did not breach Britain's treaty obligations."

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