THERESA May has been told her Brexit proposals need to be “reworked” as time runs out to reach a deal with the European Union.

Donald Tusk, the European Council president, said the Chequers blueprint was a “welcome evolution” in the UK’s approach, but major issues remained to be resolved including avoiding a hard border in Ireland and the future trading relationship between Britain and the EU.

He warned there was “less and less time” to reach a deal before the UK’s March 29 2019 exit date and confirmed he would propose an emergency EU Brexit summit in November.

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His comments came as the PM prepared to address her EU counterparts at a meeting in Salzburg, the first such gathering since the Chequers plan was published.

The Austrian summit comes days after it emerged the UK Government asked the EU to rule out Scotland getting to have any special Brexit arrangement given to Northern Ireland.

Scottish Brexit Secretary Mike Russell has said he intends to raise the matter as a matter of urgency.

His intervention followed a leak of papers from Brussels negotiators that the EU was edging towards a deal with the UK over Northern Ireland that would use technology to create a frictionless border. The arrangement would maintain close alignment with the single market.

A newspaper report said the leak stated the solution was “specifically phrased for Northern Ireland so that it is not applicable for Scotland. A UK concern.”

May will use the meeting to say that now the UK has shown it is willing to “evolve” its position, the EU must also be prepared to show flexibility.

But, in a blow to her efforts to persuade fellow leaders of the viability of her plan, it emerged her former Brexit secretary David Davis has described Chequers as a “non-starter”.

In extracts of a speech he plans to deliver in Munich today, Davis said the PM’s plan crossed all of her own negotiating red lines.

And he said: “Chequers is devoid of democracy altogether. This is why many of us will shortly be presenting an alternative plan which will outline a more ambitious vision.”

Tusk told reporters in Salzburg: “The Brexit negotiations are entering the decisive phase.

“Various scenarios are still possible today but I would like to stress that some of Prime Minister May’s proposals from Chequers indicate a positive evolution in the UK’s approach, as well as the will to minimise the negative effects of Brexit.”

Those positive areas included foreign and security policy co-operation, he said.

But in a blow to May’s approach, he said: “On other issues such as the Irish question or the framework for economic co-operation the UK’s proposals will need to be reworked and further negotiated.

“Today there is perhaps more hope, but there is surely less and less time,” he added, as he confirmed he would propose a mid-November summit.

Efforts to find an acceptable way to avoid a hard border in Ireland suffered a further setback as May’s DUP allies poured cold water on the latest EU offer.

Ahead of the summit in Austria, the EU’s chief negotiator Michel Barnier said he was ready to come forward with a new offer on the Irish border .

In order to “de-dramatise” one of the main obstacles to a withdrawal deal agreement, Barnier suggested arrangements could be made to conduct the majority of checks on imports and exports away from the border itself.

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But the Democratic Unionist Party, which has propped up May’s minority administration in Westminster since the 2017 General Election, dismissed Barnier’s proposals as unpalatable, because they would involve a customs border between Northern Ireland and the rest of the UK.

“It still means a border down the Irish Sea although with different kinds of checks,” said the party’s deputy leader Nigel Dodds.

“The fact is that both Theresa May and the Labour Party have said no British prime minister could accept such a concept. It is not just unionists who object.”

The Department for Exiting the EU welcomed the commitment by Brussels to resolving the key issue, but stressed Britain “could not accept Northern Ireland being separated off from the UK customs territory”.

May is also expected to use the Salzburg summit to hold formal face-to-face talks with Ireland’s taoiseach Leo Varadkar and Tusk today.

She may talk to other leaders in the margins of the summit in an effort to win further backing for a plan which has met fierce resistance from within the ranks of her own Conservative Party.