Britain must strike a strong trade deal with the European Union after Brexit and avoid becoming a subordinate state of the bloc, foreign minister and leading Brexiteer Boris Johnson has told the Sunday Times newspaper.

Failure to ditch EU law would make the United Kingdom a "vassal state," Johnson said in an interview published yesterday. The government must aim to "maximize the benefits of Brexit" by getting divergence from the bloc's rules so that it could do "proper free trade deals" with other countries.Prime Minister Theresa May this week secured an agreement with the EU to move Brexit talks on to trade and a transition pact. But she must now unite her deeply divided cabinet over what trade deal Britain actually wants.

Separately, in a measure of the difficulty May will face in bringing her side together, finance minister Philip Hammond caused a stir amongst some Brexit supporters because he said that after Britain formally leaves the EU in March 2019, it will seek to replicate the current status quo in a transition period.

Former work and pensions minister Ian Duncan Smith criticized Hammond, as did other leading Brexit supporters, for making a statement which he said was "not government policy."

Johnson told the Sunday Times he would advance the case for a "liberal Brexit" in a new intervention in the debate this week in which he would play up the advantages of leaving the EU.

British PM May has hit back at critics of her handling of Brexit, writing in the Sunday Telegraph that she had "proven the doubters wrong" after securing an interim deal.

Pressure lifted on the embattled leader after she struck a deal with the European Union over Britain's divorce terms last Friday, enabling talks to turn to the country's future trading relationship after months of fraught negotiations.

"We have proven the doubters wrong and are making progress towards a successful exit from the EU," she wrote in the center-right broadsheet, calling the agreement "a watershed" in negotiations, according to AFP.

A poll has found that 51 percent of Britons would now keep European Union membership while 41 percent want to leave the bloc, a near reversal of last year's referendum result, as reported by Reuters.

The BMG poll of 1,400 people for The Independent published on the newspaper's website on Saturday came as Britain moves into a second phase of negotiations on exiting the EU, which will focus on trade. The Independent said the lead for "remain" over "leave" was the biggest in any poll so far since the vote in June 2016.

But the head of polling at BMG, quoted in the Independent, said that the reason for the change was a shift in opinion among those who did not vote in last year's referendum, while around nine in 10 "leave" and "remain" voters were unchanged in their views. The survey was carried out from December 5 to 8. In the referendum last year, 52 percent of Britons voted to leave the EU and 48 percent voted to remain.