Millions more people in England are to be plunged into the toughest tier 4 restrictions from Boxing Day, it has been confirmed, as the government grapples to contain the “dangerous” spread of the new Covid variant. After ministers met on Wednesday morning to hammer out plans to combat the rising number of infections, the health secretary, Matt Hancock, announced that a series of locations in tier 2 – including Oxfordshire, most of Hampshire, West Sussex, the remainder of East Sussex not already in tier 4, as well as Brighton and Hove, Suffolk, Norfolk and Cambridgeshire – would be placed under the toughest curbs on Saturday. Parts of Essex not already in tier 4 and Waverley, in Surrey, will join them. The 6 million people living in the areas join nearly 18 million people in London, the south-east and east of England who have endured tier 4 “stay at home” restrictions – including the closure of non-essential shops and strict one-on-one meeting limits outside between households – since Sunday. “Just as we’ve got a tiered system in place that was able to control this virus, we’ve discovered a new more contagious virus, a variant that is spreading at a dangerous rate,” Hancock told a Downing Street press conference, as he unveiled the latest moves and acknowledged that tier 3 measures were not enough to control the variant. Separately, Hancock revealed that two cases of another new variant of Covid-19 linked to South Africa have been identified in the UK. The health secretary, who said cases and close contacts of cases were being quarantined in the UK and immediate restrictions were being imposed on travel from South Africa, added: “This new variant is highly concerning because it is yet more transmissible and it appears to have mutated further than the new variant that has been discovered in the UK.” Explaining Downing Street’s tier changes, Hancock, who said cases had risen 57% across the country in the last week with nearly 19,000 in hospital with Covid – almost as many as at the peak – said: “Against this backdrop of rising infections, rising hospitalisations and rising numbers of people dying from coronavirus it is absolutely vital that we act. We simply cannot have the kind of Christmas that we all yearn for.” He added: “We know that the three-tiered system worked to control the old variant and is working now in large parts of the country, especially in northern England. But we also know that tier 3 is not enough to control the new variant. This is not a hypothesis, it is a fact and we’ve seen it on the ground.” Among other changes, Hancock said Bristol, Gloucestershire, Somerset including the North Somerset council area, Swindon, the New Forest district and Northamptonshire, as well as Cheshire, Warrington and the Isle of Wight, would be moved up to tier 3. Cornwall and Herefordshire are being placed in tier 2. Hampshire’s move to tier 4 includes Southampton, Hancock said. Ahead of the announcement, a briefing for MPs with the health minister Nadhim Zahawi descended into chaos when some were unable to join because of a 100-person limit on the Zoom call. It comes after it emerged on Wednesday that the estimated “R” number – the average number of people to whom one infected person will go on to spread the virus – has risen to between 1.1 and 1.3, up from 1.1 and 1.2 last week. Wales, Scotland and Northern Ireland have announced their own strict nationwide restrictions in recent days in an attempt to contain the new variant, which is said to be up to 70% more infectious. Earlier on Wednesday, the communities secretary, Robert Jenrick, said the government did not plan to impose a third national lockdown in England but that it wanted to make sure the tiered system was “sufficiently robust” to get the disease under control. Describing the variant as a “significant gamechanger”, Jenrick said it was prevalent outside London and south-east England, although it was still much more concentrated in and around the capital. “What we want to do now is just make sure that the tiered system is right, that it’s sufficiently robust, that it can withstand and do the job, which is to keep the virus under control, even in these new changed circumstances,” he added. There are nearly 1.4 million people living in Hampshire, according to the Office for National Statistics’ mid-2019 estimate. A further 907,760 people live in Norfolk, 863,980 in West Sussex, 761,359 in Suffolk, 691,667 in Oxfordshire, 653,537 in Cambridgeshire and 557,229 in East Sussex, according to the same figures.