The president of the European Commission says he does not know what sort of Brexit the UK wants, as negotiations for the country to leave the bloc continued in Brussels.

When a BBC news reporter asked if he had gained an impression of the UK's negotiating stance after a day of talks, Jean-Claude Juncker simply replied: "No," before walking away.

Theresa May offered residency rights to EU citizens after Brexit on Thursday as talks began, but did not discuss specifics of what would be required to guarantee the status of new arrivals.

Mr Juncker called the offer "not sufficient", saying Ms May had only made a "first step" towards an agreement.

Meanwhile the UK offer was dismissed as “pathetic” by a group campaigning for an estimated three million European expats living in the UK.

Under the proposals, a new so-called "UK settled status" that grants full rights to healthcare, education, welfare benefits and pensions would be available to all EU nationals who had been in the UK for five years.

Those with a shorter period of residency would be able to stay on to reach the five-year threshold and those arriving after a yet-to-be-defined cut-off date would have a “grace period” to regularise their status.

Arriving for the second day of the summit on the anniversary of last year's Brexit referendum, Ms May said EU expats should take “reassurance and confidence” from the package.

“I want to reassure all those EU citizens who are in the UK, who have made their lives and homes in the UK, that no one will have to leave. We won't be seeing families split apart,” she said.

“This is a fair and serious offer. I want to give those EU citizens in the UK certainty about the future of their lives, but I also want to see that certainty given to citizens who are living in the EU.”

But the co-chairman of the 3Million movement, Nicolas Hatton, responded: “There is something slightly pathetic about the Prime Minister's proposal which makes no reference to the detailed, comprehensive offer tabled by the EU. The Prime Minister described her proposal as fair and serious. It's neither fair nor serious.”

In pictures: European parliament Brexit discussions Show all 12 1 /12 In pictures: European parliament Brexit discussions In pictures: European parliament Brexit discussions European commission member in charge of Brexit negotiations with Britain, French Michel Barnier listens at the President of the European Commission Jean-Claude Juncker speaking at the European Parliament in Strasbourg Getty Images In pictures: European parliament Brexit discussions Frank-Walter Steinmeier, President of the Federal Republic of Germany, delivers his speech at the European Parliament in Strasbourg EPA In pictures: European parliament Brexit discussions European Union's chief Brexit negotiator Guy Verhofstadt, President of the Group of the Alliance of Liberals and Democrats for Europe (ALDE), addresses the European Parliament during a debate on Brexit priorities and the upcomming talks on the UK's withdrawal from the EU Reuters In pictures: European parliament Brexit discussions Michel Barnier, European Chief Negotiator for Brexit reacts during a meeting at the European Parliament in Strasbourg EPA In pictures: European parliament Brexit discussions Member of the European Parliament and former leader of the anti-EU UK Independence Party (UKIP) Nigel Farage wears socks with Union Jack flag at the European Parliament in Strasbourg Getty Images In pictures: European parliament Brexit discussions Nigel Farage, United Kingdom Independence Party (UKIP) member and MEP, addresses the European Parliament during a debate on Brexit priorities and the upcoming talks on the UK's withdrawal from the EU Reuters In pictures: European parliament Brexit discussions European commission member in charge of Brexit negotiations with Britain, French Michel Barnier gestures during speeches at the European Parliament in Strasbourg Getty In pictures: European parliament Brexit discussions The President of the European Commission Jean-Claude Juncker (L) speaks with European commission member in charge of Brexit negotiations with Britain, French Michel Barnier at the European Parliament in Strasbourg Getty In pictures: European parliament Brexit discussions European Union's chief Brexit negotiator Guy Verhofstadt, President of the Group of the Alliance of Liberals and Democrats for Europe (ALDE), addresses the European Parliament during a debate on Brexit priorities and the upcomming talks on the UK's withdrawal from the EU Reuters In pictures: European parliament Brexit discussions Member of the European Parliament and former leader of the anti-EU UK Independence Party (UKIP) Nigel Farage gestures during speeches at the European Parliament in Strasbourg, eastern France, on April 5, 2017. The European Parliament will on April 5 lay down its "red lines" for negotiations over a Brexit deal, on which the assembly will have the final say in two years' time. / AFP PHOTO / Sebastien BozonSEBASTIEN BOZON/AFP/Getty Images Getty In pictures: European parliament Brexit discussions German president Frank-Walter Steinmeier delivers a speech during a plenary session at the European Parliament in Strasbourg Getty In pictures: European parliament Brexit discussions The European Parliament in Strasbourg, eastern France Getty Images

German Chancellor Angela Merkel said the proposals represented “a good start” but cautioned there were “many, many other issues” before Britain could reach agreement on a withdrawal deal.

Dutch Prime Minister Mark Rutte said there were “thousands of questions to ask” about Ms May's proposals, and Austrian Chancellor Christian Kern described them as “a first step” which did not cover the situations of many EU citizens in the UK.

Belgian Prime Minister Charles Michel called it a “particularly vague proposal”. Using a Flemish phrase to describe a dubious gift, he said: “We don't want a cat in the bag. We want the rights of EU citizens to be permanently guaranteed.”

Labour's Sir Keir Starmer said the PM's plan was “too little too late”, while London Mayor Sadiq Khan said it “does not come close to fully guaranteeing the rights of EU nationals living in the UK”.

Liberal Democrat leader Tim Farron said the proposals “leave millions of people still facing unanswered questions over their futures here”.