European Commission president Jean-Claude Juncker has delivered a fresh rebuke to Theresa May over her government's handling of the Brexit process.

Mr Juncker said official papers setting out the Government's positions were not satisfactory and it was "crystal clear" that an "enormous amount" of issues needed to be settled before talks on a future trade deal could begin.

Officials from Brussels and the UK were continuing negotiations in the latest round of the withdrawal process, but Mr Juncker's comments are further evidence of the European Union's frustration with the approach being taken by the Prime Minister and Brexit Secretary David Davis.

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His comments came after Brussels' chief Brexit negotiator Michel Barnier said he was concerned about the lack of clarity and insisted "we must start negotiating seriously".

Mr Juncker said the UK "hesitates showing all its cards" but added: "I did read, with the requisite attention, all the papers produced by Her Majesty's Government and none of those is actually satisfactory.

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"So there is still an enormous amount of issues which remain to be settled.

"Not just on the border problems regarding Ireland and Northern Ireland, which is a very serious problem in respect of which we have had no definitive response, but we also have the status of European citizens living in the UK and UK citizens living on the Continent.

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"We need to be crystal clear that we will commence no negotiations on the new relationship - particularly a new economic and trade relationship - between the UK and the EU before all these questions are resolved."

Mr Juncker added: "First of all we settle the past before we look forward to the future."

Mr Davis and Mr Barnier met on Monday at the start of the latest round of talks which highlighted differences between Brussels and Whitehall over the negotiating papers produced by the UK.

Mr Barnier said: "We need UK papers that are clear in order to have constructive negotiations. And the sooner we remove the ambiguity, the sooner we will be in a position to discuss the future relationship and a transitional period."

Mr Davis insisted the UK position papers produced in recent weeks - on issues including Northern Ireland and the continued access of goods to market - were strong in detail.

He said: "They are the products of hard work and detailed thinking that has been going on behind the scenes not just the last few weeks, but for the last 12 months, and should form the basis of what I hope will be a constructive week of talks."

Meanwhile, Labour's new Brexit stance was branded chaotic by one of the party's Leave-supporting MPs.

Blackley and Broughton MP Graham Stringer hit out at a sudden policy shift announced by shadow Brexit secretary Sir Keir Starmer committing the party to keeping the UK in the single market and customs union for up to four years after EU withdrawal in March 2019.

Mr Stringer told the BBC: "What Keir said seems completely at odds with what the leader of the party, the shadow chancellor of the exchequer, have said.

"They have made it quite clear that we cannot honour the decision of the referendum if we remain in the customs union and the single market.

"So, I think it's a bit of chaos at the centre of the party - makes no sense to me whatsoever."