The prime minister has vowed to focus on “levelling up the country” and “spreading opportunity”, after securing the post-Brexit trade deal this week.
Boris Johnson told the Sunday Telegraph the deal would provide new legislative and regulatory freedoms to “deliver for people who felt left behind”.
But fishermen’s leaders have accused him of “caving in” and sacrificing their interests to reach the agreement.
MPs will vote on the deal in Parliament on 30 December.
The agreement was reached on Christmas Eve after months of fraught talks on issues such as fishing rights and business rules.
Scrutiny of the treaty began in earnest on the morning of Boxing Day when the 1,246-page document was officially published, with Conservative Eurosceptics among those promising to pore over the details of the accord.
In his first interview since the deal was agreed, Mr Johnson said “big changes” were coming, declaring “it is up to us now to seize the opportunity of Brexit”.
He said a “great government effort” had gone into the plans, with animal welfare, data and chemicals being areas where the UK could diverge from EU standards.
“This government has a very clear agenda to use this moment to unite and level up and to spread opportunity across the government,” Mr Johnson added.
The prime minister insisted he had been willing to go for no deal when negotiations had been going in the wrong direction.
He also said the deal could withstand the “most ruthless scrutiny” from the European Research Group of Conservative Brexiteers.
The group has assembled 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.
Senior Conservative backbencher Sir Bill said “sovereignty is the key issue” as his team analysed the small print of the deal.
What happens next with Brexit?
And writing in the Mail on Sunday, Chancellor Rishi Sunak said next year would begin a “new era” for the nation as he pledged invest in infrastructure and reward “risk-takers and entrepreneurs”.
He said: “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.”
But the National Federation of Fishermen’s Organisation (NFFO) 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”.
Barrie Deas, chief executive of the NFFO, said Mr Johnson had “sacrificed” fishing to other priorities, after the subject proved to be an enduring sticking point during negotiations.
“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.
Senior UK negotiators have admitted to compromising “somewhat” over fish, although they say the EU also made concessions.
Scotland’s First Minister, Nicola Sturgeon, accused the government 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.
After this, the UK would be free to reduce EU access to its coastal waters further but could face retaliatory action.
Government sources have said any measures taken by the EU would have to be proportionate and would be limited to the fishing industry.
Meanwhile, the EU’s 27 member states indicated they will within days give their formal backing to the deal, which covers about £660bn of trade to allow goods to be sold without tariffs or quotas in the EU market.