SPAIN has risked sparking a fresh row in the Brexit talks by calling on Theresa May to stage a second referendum.

Prime Minister Pedro Sanchez said Britain should hold another vote, but only with a view to rejoining the bloc after it has left.

He told Politico: "If I was Theresa May I would call a second referendum, no doubt.

“I don’t mean now, but in the future, so that it can come back to the EU. In another way, but back into the EU.”

But the socialist leader's intervention enraged Brexiteers who accused him of meddling. Eurosceptic MEP Diane James fumed: “It’s none of his business.”

It comes after previous pleas from the leaders of Malta and the Czech Republic for a re-run of the 2016 referendum.

Mr Sanchez said both sides are "on the verge" of sealing a Brexit deal but that doors should be left open for a possible UK return.

British and EU negotiators worked over the weekend and until 3am on Sunday night in a bid to try and secure a breakthrough this week.

But the talks are still plagued by the thorny issue of the Irish border, with Germany and France playing hardball over a UK-wide customs solution.

Michel Barnier briefed EU27 ministers in Brussels that "intense negotiating efforts continue, but an agreement has not been reached yet".

Paris has ruled out granting Britain a clean get-out clause from the backstop, saying one could only be triggered with the say-so of both sides.

Europe minister Nathalie Loiseau said: "We'll have a close look at what a Customs Union would mean for us. We're ready, we're open but of course we want to see the details.

"If we end any sort of temporary arrangement this is to be a bilateral decision from the EU27 and from the UK at the same time, and we have to know in that moment what sort of solution there is for the Irish border."

Her German counterpart Michael Roth warned: "The room for manoeuvre is very much limited. Our British friends know exactly where our discussions are."

A number of states want concrete pledges from Downing Street over the application of EU labour and environmental law and ongoing fishing rights.

The Sun revealed last week that Brussels sees the terms and conditions attached to a UK-wide customs fudge as the "baseline" for a trade deal.

A Commission spokesman said today: "Intense negotiations are ongoing at technical level. We’re not yet there."