Angela Merkel has urged other European countries to force any travellers from the UK to quarantine in a move that could threaten the Government’s plans to open foreign travel to vaccinated holidaymakers.

The German chancellor said she would like other European countries to require people entering them from countries with high levels of the Indian or delta Covid variant – like Britain – to go into quarantine, as is the case in Germany.

"In our country, if you come from Great Britain you have to go into quarantine – and that’s not the case in every European country, and that’s what I would like to see," Mrs Merkel told the Bundestag lower house of parliament.

Germany currently bans anyone entering from Britain unless they are a German citizen, a resident or their spouse, partner or child or if there is an "urgent humanitarian reason" such as a family bereavement.

People from Britain who are allowed into Germany have to register to get permission to visit and quarantine for 14 days without any possibility of early test and release.

Mrs Merkel’s appeal comes amid growing concern in Europe over the spread of the delta variant, which is now dominant in Britain.

Where is the Indian (Delta) variant in the UK?

It comes just a day before the Government is due to unveil its proposals to allow double-vaccinated Britons to travel to amber countries without having to quarantine for 10 days on their return.

The vaccination scheme is expected to take effect in August, although some ministers, Tory MPs and travel industry chiefs are urging Boris Johnson to bring forward the date to July 19 to coincide with the proposed lifting of domestic restrictions.

If other countries heed Mrs Merkel’s call, it could limit vaccinated Britons’ holiday options even further. Italy has imposed a five-day quarantine on British travellers because of concern over the delta variant, while the US currently bans UK tourists as it fights a surge in delta cases.

Dr Anthony Fauci, the top infectious disease expert in the US, said the variant was now the greatest threat to US efforts to eradicate the virus. Last week, he suggested travel between the UK and US would only open up in September.

The delta variant has become dominant in Portugal and appeared in clusters across Germany, France and Spain, prompting European health officials to warn further action is needed to slow its spread. 

While the strain still only accounts for a fraction of the total virus cases in mainland Europe, it is gaining ground. It accounted for 70 per cent of sequenced cases in the greater Lisbon region of Portugal this month, up from around 10 per cent in May, according to the Portuguese health ministry.

It also accounted for more than 20 per cent in Italy and about 16 per cent in Belgium, according to a Financial Times analysis of global genomic data from the virus tracking database Gisaid.