French President Emmanuel Macron has suggested the UK could get a special trade deal with the EU after Brexit.
But he warned that Britain would not have full access to the single market without accepting its rules.
Speaking to Andrew Marr, he warned – as Brussels has already done – that the UK could not “cherry-pick” the elements it liked.
A deal might fall somewhere between the single market and a trade agreement, he said.
Mr Macron’s comments come after his first visit to the UK since becoming French president, where he held talks with Prime Minister Theresa May.
In the interview, to be broadcast on Sunday, the leader said that the UK should not gain access to the single market without accepting its “preconditions”, which include freedom of movement across the EU, budget contributions and the jurisdiction of the European Court of Justice.
“There should be no cherry-picking in the single market because that’s a dismantling of the single market,” he said.
“As soon as you decide not to join the [EU] preconditions it’s not a full access.
“What is important is to not make people believe that it is possible to [have your cake and eat it].”
He added the access to the EU for the UK’s financial services sector would be inferior to what it is now if the UK did not accept the obligations of the single market.
‘Bespoke deal is possible’
By Alex Forsyth, political correspondent
Theresa May has repeatedly said the UK wants a bespoke trade deal with the EU after Brexit rather than a replica of any existing model.
President Macron suggested that was possible, and said he hoped the deep and special partnership the Prime Minister seeks with the EU would become reality.
But he echoed a warning already stated by Brussels; if the UK wanted full access to the single market it would have to accept its rules – including the jurisdiction of the European Court of Justice – and pay in to the EU budget.
On his first visit to the UK this week, President Macron signed a treaty with Theresa May to speed up the processing of migrants in Calais.
Mrs May praised the “uniquely close relationship” between the two nations.
She said both leaders remained committed to the “Le Touquet” border agreement in Calais – the UK has announced an extra £44.5m to be spent on beefing up Channel border security.
The visit was punctuated by a smiling selfie taken of Mr Macron and Mrs May, at an evening reception in the Victoria and Albert Museum.
During the trip there was chatter about whether UK Foreign Secretary Boris Johnson had discussed building a bridge across the English Channel, between France and the UK.
But Downing Street has said there are “no specific plans” for such a project.
The full interview with French President Emmanuel Macron will be broadcast on The Andrew Marr Show on Sunday at 09:00 GMT. You can watch it on BBC iPlayer after it is broadcast.