Theresa May has put Britain on track for a "hard Brexit" by the spring of 2019, as she insisted she will not accept any limits on the UK's ability to control its own borders.
The Prime Minister's declaration that the UK will "make our own decisions" on immigration put her on collision course with the Brussels institutions and the 27 remaining member states, ahead of two-year withdrawal talks due to be triggered by the end of March 2017.
European Council President Donald Tusk said other EU states would act to safeguard their own interests, while Maltese Prime Minister Joseph Muscat - who will be president of the Council when Mrs May kicks off talks by invoking Article 50 of the EU treaties - said the single market's four freedoms of goods, services, capital and people "cannot be decoupled".
Taking the unusual step for a Tory leader of addressing the annual Conservative conference on its opening day, Mrs May confirmed plans for a Great Repeal Bill to overturn the 1972 Act which took the UK into what was then the European Economic Community.
She said Article 50 would be invoked "soon", and no later than the end of March next year.
And she rejected the argument Britain must choose between "hard Brexit" - in which the nation regains control over immigration but loses full access to the European single market - and "soft Brexit", under which access to the single market comes with a requirement to allow free movement of EU workers.
To loud applause, Mrs May said: "I know some people ask about the 'trade-off' between controlling immigration and trading with Europe. But that is the wrong way of looking at things.
"We have voted to leave the European Union and become a fully independent, sovereign country. We will do what independent, sovereign countries do. We will decide for ourselves how we control immigration. And we will be free to pass our own laws."
We have voted to leave the European Union and become a fully independent, sovereign country. We will do what independent, sovereign countries do. We will decide for ourselves how we control immigration. And we will be free to pass our own laws.
Liberal Democrat leader Tim Farron branded Mrs May's announcement a "disaster" that would mean "no single market for Britain".
But Mrs May insisted she would strike a deal allowing "free trade in goods and services" and giving British companies "the maximum freedom to trade with and operate in the single market and let European businesses do the same here".
And Brexit Secretary David Davis said EU leaders should "think carefully" before erecting barriers to trade.
Describing talk of Britain being subjected to trade barriers, such as tariffs, as "bluster", Mr Davis said: "It certainly won't be to anyone's benefit to see an increase in barriers to trade, in either direction.
"So, we want to maintain the freest possible trade between us, without betraying the instruction we have received from the British people to take back control of our own affairs."
CBI director-general Carolyn Fairbairn said business needed "urgent answers" on barrier-free access to EU markets.
She said: "Businesses cannot continue to operate in the dark. The decisions they face today are real and pressing.
"The Government's desire to play its negotiating cards close to its chest must be tempered by clear indications on how we will trade with the UK's most important partner, and how firms will be able to employ the people needed to drive growth."
Mrs May said there would be "no unnecessary delays" to Brexit talks but added she would not give a "running commentary" on their progress.
The Great Repeal Bill will transpose EU laws applying to the UK into the domestic statute book at the moment of withdrawal, so they can subsequently be amended or abolished by the UK Parliament as required, she said.
She dismissed the argument that the outcome of negotiations should be subject to a second public vote, and said: "Come on. The referendum vote was clear, it was legitimate, it was the biggest vote for change this country has ever known. Brexit means Brexit and we are going to make a success of it."
Attorney General Jeremy Wright will next week go to court to fight legal moves to secure a parliamentary vote on invoking Article 50, which was no more than an attempt to delay Brexit, she said.
And she insisted that, while she will "consult and work" with devolved administrations in Scotland, Wales and Northern Ireland, it would be for the UK Government alone to negotiate a deal, and there will be "no opt-out from Brexit" for any of the four nations of the UK.
Mrs May said Brexit would not cut the UK off from the rest of the world, but would transform it into "global Britain, a country with the self-confidence and the freedom to look beyond the continent of Europe and to the economic and diplomatic opportunities of the wider world".
There is already "abundant evidence" that foreign countries and multi-national businesses are interested in trade and investment opportunities with a post-Brexit UK, said the Prime Minister.
Foreign Secretary Boris Johnson said " any lingering gloomadon-poppers" should now accept Brexit will liberate the UK " to be more active on the world stage than ever before".
Mrs May said she expected a post-Brexit Britain to co-operate with the remaining EU on law enforcement and counter-terrorism work, while Mr Johnson said the UK would remain committed to inter-governmental work on issues such as sanctions on Russia, and the Mediterranean migration crisis.
"A truly Global Britain is possible and it is in sight," said Mrs May.
"Let's ignore the pessimists, let's have the confidence in ourselves to go out into the world, securing trade deals, winning contracts, generating wealth and creating jobs."