Britain's opposition Labour Party has said the government should consider pausing the return of university students until an "effective, efficient testing system" is put in place.

Thousands of university students have been forced to self-isolate in their bedrooms following a surge in cases of the novel coronavirus at institutions across the United Kingdom including Glasgow, Manchester Metropolitan and Edinburgh Napier.

Students returned to universities across the country this month ready for the new term, but many now fear new restrictions may last through the winter and mean they will not be able to return home for the Christmas holidays.

ITV News reported that up to 1,700 students at Manchester Metropolitan, and hundreds more at other institutions, are being prevented from leaving their accommodation blocks by security guards.

Labour's shadow education secretary, Kate Green, said the start of term should be delayed.

In a letter to the government, Green said: "We do think it is important that students have a choice. If they feel they are going to be safer at home then they should be able to stay at home and conduct their learning remotely."

Green said the government had "let young people down with the exam fiasco over the summer, and now many of those same students are being let down again".

She added in a statement: "The government should also consider a delay to the start of term or a pause in migration for universities where term has not yet begun to allow improvements in testing capacity and remote learning provision".

Speaking on the BBC's Andrew Marr Show on Sunday, Labour's David Lammy, shadow justice secretary, said there were financial implications for universities to consider. "The balance of higher education in this country is not just students, it is also to make sure we have universities in two years' time," he said.

Government scientific adviser Mark Walport last week warned that in order to stop the virus spreading to older relatives, students in virus hotspots might be forced to stay on campus.

Speaking on Sky News' Sophy Ridge on Sunday, Culture Secretary Oliver Dowden was not able to guarantee students would be able to return home.

He said: "I very much want students to be able to go home at Christmas, and if we all pull together and observe these new rules, we follow the guidance, then we will be able to get to a point where that should be possible."

A Department of Education spokesperson said the government was working closely with universities in England to ensure they were well prepared for students to return and would continue to monitor the situation, and public health advice.

Education is devolved across the UK, meaning governments in Scotland, Wales and Northern Ireland control their own universities.

Scotland's First Minister Nicola Sturgeon said last week: "no one should be under the impression that it is just a university problem". She added: "Transmission is increasing across the country and started before universities returned."

There have been more than 400,000 confirmed cases in the UK and more than 40,000 people have died, according to government figures. There were 6,042 new cases and 34 fatalities reported on Saturday.

Two leading supermarkets in the UK have reintroduced purchasing limits on items such as flour, pasta, rice, bacteria wipes and toilet paper to discourage stockpiling as fears of panic buying grow, ITV News reported.

A spokesperson for Tesco said: "We have good availability, with plenty of stock to go round. To ensure that everyone can keep buying what they need, we have introduced bulk-buy limits on a small number of products."

Morrisons had already introduced limits on certain items amid a rise in demand following the tightening of restrictions.

The Spanish government has urged authorities in Madrid to enforce a full lockdown across the capital after the city only extended partial restrictions on Friday in districts with high infection rates.

"Madrid is in a situation of serious risk and it's time to act with determination," Health Minister Salvador Illa said at a news conference on Saturday.

Confirmed cases rose by 12,272 on Friday to 716,481, the highest number in Western Europe. More than 31,000 people have died from COVID-19.

People in Spain were not allowed to leave their homes from March until May, but since restrictions were lifted on June 21 the pandemic has surged again.

France closed all restaurants and bars in the city of Marseille on Saturday, following a recent upsurge in cases nationwide. France's health service on Saturday recorded 14,412 new cases over the previous 24 hours.