Her intervention came ahead of a key meeting on Thursday at which Boris Johnson is expected to approve plans for fully vaccinated people to be able to travel to amber list countries later this summer and not be subject to quarantine when they return home.
The Balearic Islands, Malta and some Caribbean islands could also be added to the green list.
Mrs Merkel said European countries should require travellers from nations with high rates of the highly transmissible Indian or delta variant to self-isolate, 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.
New EU-wide rules will be introduced next week to facilitate the resumption of travel, which will allow vaccinated people to move freely within the Schengen area. However, individual countries can set their own tougher rules, and several – including Germany, Italy and Poland – are introducing quarantine for Britons.
Other popular holiday destinations including Greece and Spain are welcoming British tourists who have been vaccinated, and are likely to defy the German call amid fears over the devastating economic impact of losing another summer season.
It is not clear whether France will toughen its requirements for entry from Britain.
Some British sources suspect Mrs Merkel is preparing to blame Britain for the inevitable resurgence of Covid in Germany, which is months behind the UK with its vaccination programme.
Delta has become the dominant variant in Portugal and emerged in clusters in Germany, France and Spain. On Wednesday, the EU’s disease control agency called for swifter vaccination as it forecast that the variant would account for 90 per cent of all cases in member states by the end of August.
In a meeting with Ursula von de Leyen, the European Commission president, Mrs Merkel demanded common EU rules on travel and said the increase in cases in Portugal showed that a failure to do that “has now struck back”. Portugal was temporarily on the UK’s quarantine-free green list before being axed.
If other countries heed the German chancellor’s call to bar Britons, it could significantly decrease their holiday options. Germany only accepts people from the UK for “humanitarian reasons” such as a family bereavement and has mandatory 14-day quarantine for any Germans travelling from the UK.
The US currently bans UK tourists amid a surge in delta variant cases and its top infectious disease expert, Dr Anthony Fauci, has signalled that the US is unlikely to open a travel corridor with Britain before September. Government sources believe the US is “reluctant” to restore transatlantic travel.
Senior Tory MPs and travel chiefs warned that Mrs Merkel’s comments were “unhelpful” and threatened further job losses in the UK by wrecking hopes of restarting international travel.
Henry Smith, the Tory chairman of the all-party Future of Aviation group, said: “Angela Merkel’s comments are unhelpful and going in the wrong direction. It will undoubtedly have an impact.
“We need to be looking to reopen international travel, particularly for those who are fully vaccinated. The vaccine is demonstrating it is effective against new variants. It is a reality that there will be new variants going forward.”
Paul Charles, the chief executive of travel consultancy the PC Agency, said Mrs Merkel’s comments played into the sceptics’ arguments that there were “still many risks out there and Britons should not be going abroad, which will only further damage the travel industry”.
It would mean inbound foreign tourists from amber countries would still have to self-isolate for 10 days on arrival even if fully vaccinated and would only join the scheme later.
Sources said the Government wanted to avoid a “massive spike” in tourism, which means ministers are also expected to urge vaccinated Britons not to rush out and book holidays and instead travel “where necessary”.
There are also tensions over the Foreign Office’s advice on travel, which currently recommends against all but essential travel to most of Europe, including France, Spain, Italy and Greece. This invalidates most insurance policies even if people are vaccinated.
“The Foreign Office jealously guards its right to issue the advice and Grant Shapps [the Transport Secretary] has spoken of his frustration at getting them to align it with its strategy,” said a senior industry source.
Ministers will also decide on Thursday whether to add the Balearic islands of Mallorca, Menorca, Ibiza, and Formentera, Malta and some Caribbean islands to the green list.
This would allow quarantine-free travel to them from next Monday. Just 11 countries are currently green, of which Iceland, Gibraltar and Israel are the only viable holiday destinations.