South Kesteven has been moved into Tier 4 as part of the Government decision to tighten restrictions across the country in the face of the threat from the Coronavirus variant that is spreading rapidly across the country.
A spokesperson for South Kesteven District Council said: "Unfortunately, the increased rate of infection means there really is no choice. It's disappointing that we find ourselves in this position, but the safety of residents must come first.
"By adhering to the guidelines we protect ourselves, we protect others and we will help prevent our health services from being overwhelmed.
"The roll-out of the vaccination programme offers some light at the end of the tunnel and it is vital that those who are offered appointments take them - fortunately appointments are available at the vaccination centre operating from the Meres Leisure Centre in Grantham.
"It's also important for anyone showing symptoms to book a test as soon as they possibly can. Mobile testing units regularly attend the Meres and St Martin's Park, Stamford, reducing the need for people to make long journeys and making it easier to get tested.
"These changes may be unsettling for some, but South Kesteven's residents and businesses have responded magnificently to previous lockdowns and restrictions and will do so again."
The change means the district has effectively returned to the lockdown rules of November. Under Tier 4 restrictions, non-essential retail and personal care premises must close. People must work at home wherever possible, stay local and not travel to, or leave, a Tier 4 area. while residents will be restricted to meeting one other person from another household in an outdoor public space.
Exemptions to the "stay at home" message that applied in the November lockdown, will also apply in Tier 4 - including support bubbles, childcare bubbles and children whose parents are separated.
Full details of which areas have been placed in the new Tier 4 category and what that means, along with other changes, are available at www.gov.uk/coronavirus