British Prime Minister Theresa May will today come under pressure to guarantee the rights of more than 800,000 Poles living in the UK.

She will meet with her Polish counterpart Beata Szydlo in Downing Street to discuss Brexit and defence as she prepares to trigger formal negotiations to leave the European Union at the end of March.

Mrs May, speaking ahead of the summit, said she was determined to ensure Brexit "will not weaken our relationship" as she spoke of a "new chapter" in UK-Polish relations.

"Today's meeting puts beyond doubt the common ground we share, the importance we attach to our bilateral relationship and the benefits it brings," the PM said.

"We share a clear commitment to take our cooperation to the next level and to firmly establish the UK and Poland as resolute and strategic allies in Europe."

However, she is not expected to offer any guarantees on the rights of Polish citizens currently living in the UK - although government sources say she is hopeful of securing a deal covering reciprocal rights as part of Brexit negotiations.

Mrs May has refused to guarantee the rights of EU citizens living in the UK in the wake of the Brexit vote, insisting that the government must not "reveal its hand" ahead of Brexit negotiations, which will begin when she triggers Article 50 before the end of March.

The UK-Poland summit will bring together the prime ministers of the respective countries as well as senior cabinet members, including defence and foreign ministers.

The British government will also launch a new civil society forum that will meet annually to "deepen ties" between the two nations.

UK citizens in Europe

Meanwhile, Michel Barnier, the European Union's Brexit negotiator, is also digging in his heels over any quick deal, insisting last week there would be "no negotiation without notification", adding: "My work is now focused on the EU27 (the remaining EU member states)."

The issue is creating growing tensions in the EU member states and in the UK, as millions of UK-based EU citizens and Britons in the EU fret about their status.

There are an estimated 3.3 million EU nationals living in the UK, while about 1.2 million British citizens live in the EU.

This weekend, 80 MPs wrote to Donald Tusk, the president of the European Council, urging him to get on with striking a deal on reciprocal rights as tensions grow between the UK and Brussels.

"We are extremely concerned that members of the Commission - particularly Commissioner Barnier - seem worryingly indifferent to securing reciprocal rights for our and your resident citizens," the MPs said, as they accused the EU's chief negotiator of preventing discussions on the matter between member states.

"People are not bargaining chips. Human beings are not to be traded 'tit for tat' in a political playground.

"People must come before institutions and adherence to process, European or otherwise.

"No European's expatriate's livelihood and family should be held hostage in this way, whether from the UK or the EU27."