Prominent Conservative backbenchers laid into the Government’s EU withdrawal legislation as it started its journey in the Commons, with one describing it as an “astonishing monstrosity” of a bill.

The comments came during the first round of debates regarding the European Union (Withdrawal) Bill – often referred to as the Repeal Bill – which will overturn the 1972 act that took Britain into the European Economic Community.

Its aim is to transpose relevant EU law onto the UK statute book when the UK formally leaves the EU in March 2019.

While describing the bill as “vital”, the former Conservative Attorney General Dominic Grieve said that in its current form – an “astonishing monstrosity” – he “will be in no position to support it at third reading”.

Mr Grieve went on to call the situation with the so-called Henry VIII powers – allowing the executive to bypass normal parliamentary scrutiny to transpose EU law onto the UK statute book – as “frankly ridiculous”.

Nicky Morgan, the former Conservative cabinet minister, added there is “no sign of taking back control” in the bill, adding on Twitter: “The ‘Repeal Bill’ is actually a ‘Re-introduction’ Bill – making the UK rule-takers not rule-makers.”

She added that the “true saboteurs” of Brexit are those opposed to Parliament having a role in scrutinising the process. “Parliamentary scrutiny is not an affront to democracy,” she said. “It is its very essence.”

Kenneth Clarke, the prominent Conservative MP, also warned Mr Davis that he needed “assurances” before voting for the legislation next week, adding the Government may need to “go back to the drawing board” with the bill.

“Minded as I am at the moment to contemplate voting for a second reading, I am going to need some assurances before we get there,” he said. “I haven’t decided yet [how to vote] – I’m actually going to listen to the debate, which is a very rare feature in this House.

“And if the Government isn’t going to move in the next two days of debate, well I think we may have to force it to go back to the drawing board and try again.”

In an appeal to his colleagues – and an attempt to stem any rebellion on the backbenches – the Brexit Secretary said he will “stand ready to listen to improvements to the bill” as he introduced the legislation.

He said: “This bill is an essential step, whilst it does not take us out of the European Union – that's a matter for the Article 50 process – it does ensure that on the day we leave businesses know where they stand, workers' rights are upheld and consumers remain protected.

“This bill is vital to ensuring that as we leave, we do so in an orderly manner.”

But in his forensic analysis, Sir Keir Starmer, the Shadow Brexit Secretary, said Mr Davis was keen to portray the bill as a technical one. “Nothing could be further from the truth,” he said.

He went on to say that many rights – such as those affecting working times, workers' rights, and health and safety – were protected in delegated legislation by the EU, meaning they had enjoyed “enhanced protection” for 44 years.

Yet, he said: “Under this bill, the Secretary of State says they survive and I accept that and he does have a commitment to rights at work – but they don't survive with their enhanced status – they survive only in delegated form.

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“From the date of this bill they are amendable by delegated legislation – all of those rights at work, those environmental provisions, consumer rights – they are unprotected from delegated legislation.”

During the debate Mr Davis also took a swipe at his former colleague George Osborne, prompting laughter from the Conservative benches. Labour MP Stephen Timms asked the Brexit Secretary: “George Osborne in his headline in the Evening Standard last night referred to the Secretary of State’s approach as ‘rule by decree’.”

But Mr Davis replied: “I don't read the Evening Standard, I have to tell you, and it sounds like with good reason.

“I have to tell him that if I'm going to take lectures on rule by decree, it won't be by the editor of the Evening Standard.”