Health Secretary Matt Hancock confirmed most of Essex and part of Surrey would have Covid restrictions tightened this weekend.
In a statement to the Commons he said the government would work with local leaders in to move into a high alert Tier 2 level.
Mr Hancock said: "Working with local leaders in Essex and Elmbridge, we’re also moving them into local alert level high and I want to pay tribute to the leadership of Essex County Council and in Elmbridge where they have been working so hard to suppress the virus."
Health minister Helen Whately held talks with MPs in the county on Thursday morning.
David Finch, leader of Essex County Council, welcomed Matt Hancock’s announcement that the county would be moving to the High covid alert category, “which is clear recognition of the severity of the situation we find ourselves in as a county, and indeed across many parts of the country”.
In a statement, he added: “We think the government has decided correctly, guided by the science and the fact is that the number of cases in Essex is rising exponentially.
“We understand that the move to the High local covid alert level may affect people’s lives and businesses and understand the very strong feelings about this. However, we have a duty of care to the people of Essex, and we firmly believe that this is the best route to minimise disruptions, to save lives – not just for those with the virus, but for other patients as well – and to protect businesses.
“These are difficult times for individuals, businesses and communities, but I know that as a county we will come together to support and protect one another – as we have done previously – and that acting sooner rather than later to curb the spread of Covid is the right thing to do.”
Southend and Thurrock are unitary authority areas and will remain in Tier 1 of the Covid restrictions.
Retired NHS staff are on standby to help in the event of a surge in demand for hospital beds, Health Secretary Matt Hancock said.
Responding to a question from Tory MP Dr Ben Spencer (Runnymede and Weybridge), Mr Hancock said: “The expansion of NHS capacity is of course critical, as is controlling the virus, both of them.
“In London, we have not yet had to stand up the NHS Nightingale again, which is at the ExCeL Centre. We stand ready to do so if necessary.
“We now have a huge quantity of ventilators, we have the Nightingales for bed capacity and we have brought more people back into the NHS over the last six months and we have people on standby, retired NHS staff.”
Harlow MP Robert Halfon said he welcomed Tier 2 measures for Essex but would call on Chancellor Rishi Sunak to prevent businesses suffering financially from the move.
The senior Conservative MP said: “I’ve worked hard with Essex council and Public Health England officials and the ministers at the department of health on these issues.
“Sadly I support the Tier 2 measures, if Essex does go into them, because otherwise if we don’t act early we could face a situation, a real struggle, that sadly so many northern towns and cities are facing at this time.
“I will be writing to the Chancellor to ensure that, as far as possible, alongside the existing scheme, that businesses do not suffer financially because of the move to Tier 2.
“The key issue is if we don’t do this now we could face the much higher restrictions in a few weeks which would be even worse for businesses.”