Boris Johnson has touted post-Brexit changes to business taxes and regulation next year as Conservative Eurosceptics pored over the details of his trade agreement with the EU.

The Prime Minister said that Chancellor Rishi Sunak is “doing a big exercise on all of this” currently but insisted that the UK would not regress on workers’ rights or environmental standards.

Scrutiny of the treaty began in earnest when the 1,246-page document was officially published on the morning of Boxing Day – less than a week before its implementation.

It was quickly met with severe criticism from those working in the fishing industry who said they had been “sacrificed” in order to secure the deal with Brussels.

The Prime Minister says that, although he accepts that “the devil is in the detail” of the deal, he believes that it will stand up to inspection from the European Research Group (ERG) of Brexiteers.

The group has convened a self-styled “star chamber” of lawyers led by veteran Eurosceptic MP Sir Bill Cash to examine the full text ahead of a Commons vote.

All that’s really saying is the UK won’t immediately send children up chimneys or pour raw sewage all over its beaches. We’re not going to regress, and you’d expect that

In an interview with the Sunday Telegraph in the hours after brokering the deal on Thursday, Mr Johnson said that “a great Government effort” has gone into compiling plans for when the Brexit transition ends on December 31.

But he said it “perhaps would not have been fruitful” to discuss them publicly during negotiations, as he listed animal welfare regulations, data and chemicals alongside existing plans to establish low tax freeports.

The deal contains commitments not to regress on standards for workers’ rights and environmental standards, which is a bone of contention for some Brexiteers.

However, Mr Johnson said: “All that’s really saying is the UK won’t immediately send children up chimneys or pour raw sewage all over its beaches. We’re not going to regress, and you’d expect that.”

The Prime Minister added that his Chancellor is “doing a big exercise on all of this” in regards to business taxes and regulation as he seeks to use the “legislative and regulatory freedoms to deliver for people who felt left behind”.

Mr Sunak said next year would begin a “new era” for the nation as he pledged to invest in the nation to “build opportunity for everyone” in investing in infrastructure and “rewarding risk-takers and entrepreneurs”.

“I want next year to be the start of something much more meaningful for all of us. A moment to look afresh at the world and the opportunities it presents, and to consider how to take advantage of them,” the Chancellor wrote in the Mail on Sunday.

Senior Conservative backbencher Sir Bill said “sovereignty is the key issue” as his team analysed the small print of the deal, but there were indications senior Brexit hardliners were preparing to support the deal, despite being angered by the little time they have to debate it.

No 10’s chief negotiator Lord Frost hailed the deal as beginning a “moment of national renewal” that he argued means the UK “sets its own laws again” by ensuring there is “no more role” for the ECJ.

However, the chief executive of the National Federation of Fishermen’s Organisation (NFFO), Barrie Deas, accused Mr Johnson of having “bottled it” on fishing quotas to secure only “a fraction of what the UK has a right to under international law”.

Mr Deas said the Prime Minister had “sacrificed” fishing to other priorities, with the subject proving to be an enduring sticking point during negotiations as they raced to get a deal by the end of the transition period on December 31.

“Lacking legal, moral or political negotiating leverage on fish, the EU made the whole trade deal contingent on a UK surrender on fisheries,” Mr Deas said.

Scotland’s First Minister Nicola Sturgeon accused the Conservatives of having “sold out Scottish fishing all over again”, adding: “Promises they knew couldn’t be delivered, duly broken.”

The share of fish in British waters that the UK can catch will rise from about half now to two-thirds by the end of the five-and-a-half-year transition.

A senior member of the UK negotiating team defended the fishing compromise as a transition to a point of “full control over our waters” but acknowledged that No 10 wanted the process to happen “faster”.

Meanwhile, the EU’s 27 member states indicated they will within days give their formal backing to the deal, which covers about £660 billion of trade to allow goods to be sold without tariffs or quotas in the EU market.

MPs and peers will be called back to Westminster on December 30 to vote on the deal.

The agreement will almost certainly be passed by Parliament, with Labour supporting it, as the alternative would be a chaotic no-deal situation on January 1.