Brexit talks 'getting to the heart of the matter' as David Davis returns to Brussels

The second round of talks with the European Commission's chief negotiator Michel Barnier comes amid reports of bitter divisions in the Cabinet.

Over the weekend, Chancellor Philip Hammond angrily accused Cabinet rivals of trying to undermine his agenda for a "softer" business-friendly Brexit prioritising jobs and the economy.

One unnamed Cabinet minister was reported have hit back, claiming Mr Hammond was part of an attempt by "the Establishment" to prevent Britain ever leaving the EU.

The Daily Telegraph quoted the minister as saying: "What's really going on is that the Establishment, the Treasury, is trying to f*** it up. They want to frustrate Brexit."

The rowing will be seen as further evidence of Theresa May's weakness after seeing her Commons majority wiped out in last month's general election.

After what Mr Davis said was a "good start" in the opening session of the Brexit negotiations last month, the mood between London and Brussels has soured following a series of public spats.

It began with the publication of what Britain said was a "fair and serious" offer to guarantee the future rights of the 3.2 million EU citizens living in the UK and the 1.2 million British ex-pats in the EU.

The proposal to grant EU nationals "settled status", effectively indefinite leave to remain, was immediately dismissed by European Council President Donald Tusk as "below our expectations", and risked worsening their situation.

Foreign Secretary Boris Johnson then fanned the flames when he said in the Commons that Brussels could "go whistle" if it expected the UK to pay a hefty "divorce bill" in respect of its outstanding financial obligations.

Mr Barnier, who has made clear that he is not prepared to start talks on a trade deal until there has been sufficient progress on the financial settlement, retorted icily he could not hear any whistling, "just the clock ticking".

That row was quietly defused with a written Government statement acknowledging Britain had obligations to the EU which would continue after the UK had left and which "need to be resolved".

However ministers also faced criticism at home over their plans to withdraw from the EU nuclear regulator, Euratom, amid warnings the UK find its access to radioactive isotopes used to treat cancer restricted.

All three issues will be on the agenda for this week's discussions, which are expected to continue to Thursday, along with the thorny matter of the future border between Northern Ireland and the Republic.

Mr Davis made clear his first priority would be resolving the issue of citizens' rights, saying he was determined to make "real progress".

"We are now getting into the substance of the matter," he said.

"It's four categories really. The issue of citizens' rights, the issue of finance, the issue of separation issues and, of course, separately, Northern Ireland.

"For us it's incredibly important we now make good progress. That we negotiate through this and identify the differences, so that we can deal with them, and identify the similarities so that we can move forward.

"And now it's time to get down to work and make this a successful negotiation."

Mr Barnier added: "I look forward to our negotiations this week. We'll now delve into the heart of the matter.

"We need to examine and compare our respective positions in order to make good progress.

"As you know, our negotiating groups will work on citizens' rights, on the financial settlement and other separation issues.

"David and I will be in contact throughout the week. Rendezvous to take stock together on Thursday."