France is to heavily tighten entry conditions for people travelling both to and from the United Kingdom in order to limit the spread of the Omicron variant, the government said on Thursday.

The prime minister's office at Matignon confirmed that from midnight on Friday into Saturday, travellers will need to give "compelling reasons" in order to visit the UK and return to France, regardless of vaccination status.

A government statement cites the British government's admission that an Omicron "tidal wave" is expected to hit the country as justification for the move.

Travel for tourism and business will not be allowed, the statement says. However, "these compelling reasons will nevertheless not apply to French citizens as well as their partner and their children who will still be able to come to France," it explains.

An attached list of what constitutes "compelling reasons" for travel in both directions also includes, for the UK, a "foreign citizen joining their country".

The new measures also mean that COVID-19 tests are required to enter France within the previous 24 hours, instead of the current 48 hours. They apply to all arrivals whether or not people are vaccinated.

Matignon confirmed that the tests can be either PCR or lateral flow -- although home tests are not valid -- and proof must be in the form of a recognised certificate.

People arriving in France from the UK will also need to self-isolate, and to register their address online in advance, via an app that will generate an isolation order from the prefecture. The quarantine can be lifted after 48 hours once a negative COVID-19 test is provided.

The French government is calling on travellers who had planned to go to the UK to delay their journey.

The new measures will be "more drastic" than those which exist at the moment, government spokesman Gabriel Attal acknowledged in an interview with BFMTV and RMC earlier on Thursday.

He said that quarantine for visitors from the UK would be subject to "checks by the security forces".

The new conditions for entry into France from the UK have now been published in English by the French consulate in London.

According to the French government list, those deemed to have "compelling reasons" to visit the UK include "a foreign citizen joining their country", visits after the death of a close family member, or if such a person is in a life-threatening condition.

Those allowed to return to France include French and EU nationals and their families, as well as Britons "benefitting from the agreement" on Brexit — meaning registered UK residents in the EU — plus nationals of other countries residing in the EU.

Other exemptions to the travel ban include civil servants travelling professionally, police, customs officials and Channel tunnel workers, health workers and registered students, and transport workers including lorry drivers carrying goods. Air passengers changing planes in France can enter airport transit zones for up to 24 hours.

The announcement comes the day after the UK registered 78,610 daily COVID-19 cases — the highest number since the beginning of the pandemic as the highly transmissible new Omicron variant spreads.

British Prime Minister Boris Johnson said last Sunday that an Omicron "tidal wave" was expected to hit the country. In some areas, the number of Omicron cases is doubling every two days, he added on Wednesday.

So far, France has detected 240 Omicron cases on its territory. The new restrictions concerning the UK were designed to "tighten the net" to reduce the number of cases of the variant entering the country and slow down its spread, Gabriel Attal said.