The Foreign, Commonwealth and Development Office (FCDO) has warned Britons in France that they should be armed with their vaccination certificates or produce a negative Covid-19 test at restaurants, cafes, museums, some public transport and other venues.
It is also required for hospital visits.
It became law in France despite widespread public demonstrations.
"You need to demonstrate your Covid-19 status including vaccination status, negative test or proof of recent recovery, to access events or spaces with over 50 people attending," the FCDO said in its latest update.
"From 9 August this will apply to a wider group of leisure activities as well as some public transport."
It includes intercity trains and when visiting tourist attractions such as the Eiffel Tower.
The FCDO says from 30 September it will become mandatory for those aged 12 to 17.
Along with the passing of the new law, France also made vaccinations mandatory for healthcare workers.
Meanwhile, the UK government is facing a backbencher revolt over two issues.
Dozens of MPs have signed a declaration opposing a similar vaccine passport scheme in the UK to enter domestic venues and attend events.
There is also backbench dissent over its ‘inexplicably complicated’ decision to make France an ‘amber plus’ country.
France is the only country so far but could be joined by Spain and Greece.
It means people returning go the UK would still have to quarantine.
