Theresa May has hit back at claims that she is heading for a "Brexit in name only", declaring she recognises that voters wanted to see change in the UK's relations with Europe when they backed Leave in the 2016 referendum.
The Prime Minister repeated her promise to deliver on Brexit, pointedly noting that the 17.4 million Britons who handed victory to Leave "did not vote for nothing to change when we come out of the EU".
The comments come as the Prime Minister made clear she will fight the proposal on citizens' rights which emerged in negotiating guidelines agreed by the EU27 earlier this week.
Asked whether she believes in Brexit "hand on heart", Mrs May replied: "Yes."
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Speaking to reporters during a trip to China, Mrs May firmly rejected speculation that she might seek to extend the expected two-year transition period after the official date of Brexit on March 29 2019 to three or more years.
"People are saying 'Oh we're secretly negotiating for three years'. No. We're not," she said.
And she promised to fight Brussels proposals which would give EU nationals full citizens' rights if they come to the UK as late as the end of 2020.
There is growing disquiet among pro-Brexit Conservatives that the Prime Minister is softening her stance on the terms of the UK’s EU exit, leading to growing speculation about a challenge to her leadership.
"What we're doing now is doing the job that the British people asked the Government to do, which is to deliver on Brexit," Mrs May said.
"They want us to do that. But in doing that, they did not they did not vote for nothing to change when we come out of the EU."
She added: "When we agreed the citizens' rights deal in December, we did so on the basis that people who had come to the UK when we were a member of the EU had ... made a life choice and set up certain expectations and it was right that we have made an agreement that ensured they could continue their life in the way they had wanted to," said the PM.
"Now, for those who come after March 2019, that will be different because they will be coming to a UK that they know will be outside the EU.
"This is a matter for negotiation for the immediate period but I'm clear there's a difference between those people who came prior to us leaving and those who will come when they know the UK is no longer a member of the EU."
New leaked government analysis has revealed that a post-Brexit trade deal with the United States will not make up for economic growth lost by curbing immigration from the EU.
Border checks and the loss of market access in certain sectors on top of the impact of immigration reforms will cause the main damage to the economy, Brexit analysis prepared for the Department for Exiting the EU found.
Several immigration policies were analysed in the papers leaked to the BuzzFeed news website, assessing their impact they are likely to have on UK finances.
The research found replacing free movement with a system similar to that in place for non-EU citizens would have a bigger negative effect than the 0.2% boost to GDP growth that a US trade deal would provide.
SNP Europe spokesman Stephen Gethins said the analysis showed there would be “huge economic harm” from leaving the single market and ending free movement.
“EU nationals contribute enormously to our society, our economy and our workplaces,” Mr Gethins said.
“It is vital that the Prime Minister listens to small and large businesses who employ thousands of EU nationals – including many who work tirelessly in our frontline services, including the NHS.
“It’s now clear that this UK government is being driven by ideology, rather than protecting the UK’s economic and social interests.”
Liberal Democrat leader Sir Vince Cable said: "The view that restricting immigration is a positive thing, something this Conservative government have only encouraged, has been starkly contradicted by their own analysis.
"This analysis shows a fall in EU migration is far from cost free.
Mrs May also told journalists in China that she will discuss Britain's security relations with the remaining EU in a speech to the Munich Security Conference in Germany next month.
But she declined to say whether she would use the address as an opportunity to spell out her vision for the "end-state" she wants for Britain after Brexit.
"As and when we have more to say and to clarify, then I will do so, as I have," she told reporters.