Government to 'push ahead' with Brexit
The government will "push ahead" to triggering Brexit without Parliamentary approval, Downing Street says.
In a statement after Theresa May's cabinet gathered at Chequers, Number 10 said ministers agreed on the need for a "unique" deal for the UK.
This included controls on EU migration as well as a "positive outcome" on trade, Downing Street said.
Mrs May told cabinet colleagues the UK would not stay in the EU "by the back door".
The PM has said official talks with the rest of the EU will not begin this year.
The meeting at the PM's country residence was billed as the most significant since the referendum vote in June amid reports of tensions and diverging priorities among key figures in the Cabinet charged with implementing the UK's exit.
Cabinet ministers had been asked before the summer break to identify what were described as the "opportunities" for their departments.
In comments made at the start of the meeting while cameras were allowed in, Mrs May told ministers that the government was clear that "Brexit means Brexit".
"We will be looking at the next steps that we need to take and we will also be looking at the opportunities that are now open to us as we forge a new role for the UK in the world," she said.
"We must be clear that we are going to make a success of it - that means no second referendum, no attempts to sort of stay in the EU by the back door. That we are actually going to deliver on it."
The prime minister has said the UK government will not trigger Article 50 - the official mechanism for beginning the process of leaving the EU - until the start of 2017 at the earliest.
From that moment, discussions over the terms of the UK's exit will conclude in two years unless all 28 members of the EU agree to extend them.
The UK voted to leave the EU, by a margin of 51.9% to 48.1%, in a referendum on 23 June and Mrs May, who had backed staying in the EU, became prime minister after David Cameron resigned in its aftermath.
Two months on from the vote, the relationship the UK will have with the EU after its exit, in terms of access to the EU internal market and obligations in regard to freedom of movement, remains unclear.
A Downing Street spokeswoman reiterated that MPs would not get a vote on Article 50, and said cabinet members had agreed that the UK would not seek an "off the shelf" model for its future relationship with the EU.
"This must mean controls on the numbers of people who come to Britain from Europe but also a positive outcome for those who wish to trade goods and services," she added.
Ministers also agreed that Brexit must work for Scotland, Wales and Northern Ireland, she said, but the UK government would decide the terms and when to trigger Article 50.
Analysis by Chris Mason, BBC political correspondent
Confronting the colossal task of arranging, choreographing and negotiating the UK's withdrawal from the European Union was never going to be quick or straightforward.
But politically, the prime minister will know her holding position over the summer - that "Brexit means Brexit" - will have a sell-by date: for fellow Conservatives, the electorate and other European leaders.
That soundbite was her three-word battalion designed to reassure those who voted to leave that she - a Remain campaigner, albeit a quiet one - was committed to delivering the will of the electorate.
Today, Theresa May sought to reinforce her reassurance that out would mean out.
The crucial trade-off in the coming wrangling is likely to be between acknowledging many voters' desire to see a reduction in EU immigration, while ensuring British businesses can trade as freely as possible with our nearest neighbours.
But tonight, the timetable for, let alone the outcome of, the forthcoming negotiation is yet to be publicly set.
Former Foreign Office Minister Hugo Swire said there was a "definite fault line" between ministers who believed Brexit was chiefly about ending free movement and those who wanted to see more "flexibility", meaning the UK did not yet have its "ducks in a row" for negotiations.
Mr Swire, who campaigned for Remain, told BBC Radio 4's The World at One: "Until we have a clear idea of what it is that we are trying to achieve... I think we should proceed with great caution."
Wednesday's meeting at the prime minister's country residence is being seen as an opportunity for Mrs May and senior colleagues to talk through many issues involved ahead of this weekend's summit of G20 leaders in China.
The talks are being billed as the most significant since the referendum result and mark an end to the relative lull in proceedings over the summer recess - which ends on Monday.
Mrs May, who has held face-to-face talks with the leaders of Germany, France, Italy, Ireland, Poland and Slovakia since taking office, has said time is needed to determine the UK's strategy as a "sensible and orderly departure" is in the national interest.
But several senior Conservatives have warned against undue delay and said nothing should stand in the way of the UK triggering Article 50 as soon as possible next year.
Ex-Chancellor Lord Lawson, a leading Leave campaigner, said the UK should not try to negotiate a special trade deal with the EU, allowing it to remain within the single market, because it simply wasn't on offer on acceptable terms and would hold the process up.
"As soon as you stop wasting time trying to negotiate the unnegotiable - some special trade deal with the EU - it is possible to have a relatively quick exit," he told BBC Radio 4's Today.
Brexit-backing backbencher Jacob Rees-Mogg agreed, telling BBC Radio 4's World at One leaving the EU was "the simple bit" and that trade negotiations could take place afterwards.
Among those present at the cabinet meeting were Foreign Secretary Boris Johnson, International Trade Secretary Liam Fox and David Davis, Secretary of State for Exiting the European Union.
Mr Johnson, Mr Fox and Mr Davis are reported to have held private talks last week amid reports of early disagreements over the shape of a future Brexit settlement and departmental responsibility for trade issues.
Former Conservative minister Anna Soubry, who backed the UK remaining in the EU, said it was now up to the "three Brexiteers" to deliver the best deal for the British people.
"Boris Johnson, Liam Fox and David Davis - these are the people that have to show us the progress they have made, what Brexit is beginning to look like, what successes, difficulties or failures they have had," she told Today.
'Nods and winks'
Labour's Jon Ashworth said what was needed was a detailed statement on the work that had been done so far rather than brainstorming meetings and "nods and winks" on issues such as immigration.
The SNP, meanwhile, has accused the government of "breathtaking complacency" over a plan for Brexit and "making it up as they go along".
Chequers, an isolated 16th Century mansion 40 miles north-west of London, has played host to a number of historic occasions in the past 50 years and was one of Margaret Thatcher's favourite locations to conduct high-level meetings and personal diplomacy.
As well as the Brexit discussions, Downing Street said Chancellor Philip Hammond had updated Cabinet on the economy, and Mr Johnson had provided an update on the fight against so-called Islamic State.