Foreign Secretary Philip Hammond has said it would be "catastrophic" for Britain to lose access to the European Union's single market following the referendum vote to leave
But he said it would not be able to keep access to the single market while also asserting full control over migration from EU member states.
Speaking to ITV's Peston on Sunday, he said: "Those who say no they need us more than we need them don't worry they'll allow us to have control of migration from the European Union while maintaining access to the single market are simply mistaken."
"We will not be able to negotiate control of migration from the EU and at the same time full access to single market," he added.
"No imperative" to invoke Article 50 immediately"
There have been calls from EU leaders for Britain to invoke article 50 of the Lisbon Treaty "immediately".
But while acknowledging that "we're already under pressure", Mr Hammond insisted there is "no imperative on us to serve article 50 notice at any particular time".
"As the prime minister's made clear that will be a decision for the next prime minister after the transition has happened, " he added
Hammond not standing as Tory leader bu
Mr Hammond, who had campaigned for Britain to stay in the European Union, also he would not stand as a candidate to lead the party and the country.
But he said the new leader would have to be "somebody who has spelt out an agenda which the key Leave campaigners accept and can work with".
However, he did not endorse Boris Johnson, who is considered to be clear favourite for the role, saying "I want to see who all the candidates are".
He added: "The problem is key leave campaigners made contradictory promises to the British people. I'm sorry to say that but they did."
"Boris is one of those. They have got to make those trade-offs between the different things they promised which are mutually incompatible. That will be hugely disappointing to a lot of people in this country who voted Leave.