Live updates: follow the latest news on Covid-19 variant Omicron
Proof of coronavirus vaccination or a negative lateral flow test result will be required for spectators to attend sporting events in England with crowds of more than 10,000, after the government announced it is to implement its 'Plan B'.
Prime Minister Boris Johnson on Wednesday evening introduced new measures in response to rising cases and the spread of the Omicron variant.
He confirmed that under the new rules, which will come into effect in a week's time, for entry to any venue with more than 10,000 people, double vaccination or a negative lateral flow test result will be mandatory.
Four Premier League matches are scheduled to take place next Wednesday.
"We will make the NHS Covid pass mandatory for entry into nightclubs and venues where large crowds gather, including unseated indoor venues with more than 500 people, unseated outdoor venues with more than 4,000 people and any venue with more than 10,000 people," Mr Johnson said.
"The NHS Covid pass can still be obtained with two doses but we will keep this under review as the boosters roll out.
"As we set out in Plan B, we will give businesses a week's notice, so this will come into force in a week's time, helping to keep these events and venues open at full capacity while giving everyone who attends them confidence that those around them have done the responsible thing to minimise risk to others."
After the government's announcement, an English Football League representative said: "In light of the government's activation of Plan B Covid-19 mitigation measures, the EFL will continue to support those clubs that will be required to admit fans with Covid certification from Wednesday, December 15, onwards.
"Despite challenging circumstances throughout the pandemic, EFL clubs have readily adapted to welcome fans safely and we know clubs have been preparing for this additional layer to their matchday operations to ensure supporters can continue to watch their team play with confidence over the winter period."
A statement on Premier League team Brentford's official website said: "We note that the prime minister today announced that the Government's winter contingency strategy, Plan B, is going to be introduced in seven days.
"Clearly there will be implications for supporters attending our matches. We will be in discussions with the Premier League and local authorities over the coming days and will make further announcements in due course.
"In the meantime, we urge all supporters to follow public health guidance and wear a face covering on public transport and in crowded areas to reduce the spread of the virus."
Rising Covid-19 rates in the UK are already affecting Premier League clubs with Tottenham and Leicester having to play with depleted squads or cancel matches.
Tottenham's Europa Conference League clash with Rennes on Thursday has been postponed after a severe coronavirus outbreak at the Premier League club.
Tottenham boss Antonio Conte revealed earlier on Wednesday that eight of his players and five members of staff had tested positive for Covid-19.
It had appeared Uefa would insist on the Rennes match going ahead in north London if Tottenham had the minimum number of 13 players available, but the rapid spread of the virus forced a change of plan.
"We can confirm that our Uefa Europa Conference League Group G home fixture against Stade Rennais will not take place tomorrow after a number of positive Covid-19 cases at the club," Tottenham said.
"Discussions are ongoing with Uefa and we shall provide a further update on this fixture in due course.
"Additionally, following discussions with the Health Security Agency and DCMS advisers, the club has been advised to close the first team area of its training centre at this time, in the interests of the health and safety of players and staff.
"All other areas of the training centre remain operational."
It has been reported Tottenham are considering asking for their Premier League match at Brighton on Sunday to be postponed.
After the Brighton game, Tottenham face top-flight fixtures against Leicester on December 16 and Liverpool on December 19.
Last season, Tottenham saw matches against Aston Villa and Fulham postponed due to Covid outbreaks within the opposition.
"I think that I haven't got to send a message to anyone because the situation is very clear," Conte said of the potential for more of his team's games to be postponed.
He admitted the sudden outbreak had left his squad scared.
"To speak about football today is impossible. The last situation made me very upset," he said.
"The situation is serious. There is a big infection. Again at the end of the session, one player [tested] positive, another staff [member] positive. Tomorrow, who [will it be]?
"Now, for sure, we are a bit scared because tomorrow we don't know what happens."
Conte was not able to confirm whether it was the new Omicron variant causing the outbreak, but revealed he had been vaccinated.
"I think everyone takes best decision and it is a question for the medical department about people that whether they are vaccinated or not," he said when asked about the status of his players.
Conte was supposed to be joined by Spurs' Danish midfielder Pierre-Emile Hojbjerg at the pre-match briefing, but instead faced the media on his own.
"Every day we are having contact with the people that are false negative and become positive and then everyone is a bit scared, I think, because we all have family and why I have to take this risk?" Conte said.
"I think that it is not right for everyone because we have family and we have contact with them when we come back home.
"I understand also the worry for the players and I understand everyone that works here. The postponement gives Uefa a headache over the rescheduling of the game."
Rennes are top of Group G, while Tottenham are level on points with third-placed Vitesse Arnhem.
Another top-flight club, Leicester, will be without seven players through illness for their final Europa League group game in Italy against Napoli.
Brendan Rodgers confirmed some of the unnamed players had tested positive for coronavirus, while others had been left at home as a precaution as they felt unwell.
Belgium midfielder Youri Tielemans is back in contention after a five-game injury lay-off and left-back Ryan Bertrand is also available.