Theresa May will not be back at work until Thursday, No 10 has said – almost four weeks after she began her summer break.

The Prime Minister is expected to be still out of the country when crucial papers for the Brexit negotiations – on trade and Northern Ireland – are published, it has emerged.

Ms May had been expected back in Downing Street at the start of this week, after separate walking holidays in Italy and Switzerland.

The next few days will be crucial to hopes of a successful resumption of the EU withdrawal talks, after Brussels’s criticism that the UK position has been a muddle.

But the Prime Minister will be away for longer than expected, after interrupting her break to join the commemorations for the 100th anniversary of the Battle of Passchendaele at the end of July.

Ian Lavery, the Labour party chairman, criticised her continued absence, saying: “With her Cabinet squabbling over the Government’s position on issue after issue, it seems like she’s given up on governing.

“While the Prime Minister has taken a long break following her humiliating loss of authority at the general election, Jeremy Corbyn has been preparing to win the next election, campaigning in Tory-held marginals across the country.”

The documents to be published over the next few days could be crucial to persuading the EU that the UK is serious about meeting its tests on the divorce settlement.

Only then will negotiations on a post-Brexit trade deal – Britain’s priority – begin, the EU has insisted.

As well as uncertainty in the EU negotiations, Ms May’s holiday has also coincided with further strife in the NHS, where waiting lists are now their longest for almost a decade.

In the summer, demand for medical treatment is usually lighter, but four million people were queuing for treatment in June, underlining the service’s fragility ahead of another winter of financial squeeze.

Meanwhile, the Prime Minister has not spoken publicly on the crisis surrounding North Korea’s missile tests or Donald Trump’s promise to inflict “fire and fury" on the rogue communist state.

Her spokesman indicated on Monday that she had not been in personal contact with Washington since the threat of nuclear war loomed, but insisted the Government was in “constant contact”.

Asked if Ms May was worried about the President’s rhetoric, he replied: “We have been absolutely clear in our condemnation of North Korea and its destabilising activity.