Carlisle is to move into tier two coronavirus restrictions from Saturday, the government has announced.
Households in the city will no longer be allowed to mix indoors in any setting from midnight.
The leader of Cumbria County Council said the government had taken it by surprise, causing "confusion and chaos", and described communication of the move as an "omnishambles".
The Department of Health has been approached for comment.
Carlisle recorded 262 new cases in the week to Monday, giving an infection rate of 241 cases per 100,000 people, against the English average of 225.
Stewart Young, leader of the county council, tweeted he was "astonished to read in the press" Carlisle's level would be raised "when we were told only this morning that there would be further discussions next week".
Astonished to read in the press that Carlisle is to be moved into Tier 2 tomorrow, when we were told only this morning that there would be further discussions next week.— Stewart Young (@stewartyoung058) October 30, 2020
In a later interview with BBC Radio Cumbria, he said: "I've never had a day like it. We understood the agreement was we'd keep it under review and have further discussions on Monday so that was the position as late as this morning.
"Then we were all caught unaware because the government suddenly announced we were going into tier two at midnight so everybody was scrabbling around to find out what happened."
Mr Young said the government then informed the council it had made a "mistake" and would reverse the decision, only for another email to arrive shortly after, confirming the move to tier two would happen after all.
Mr Young, who also represents the Upperby ward on the city council, added: "It's literally been changing from minute to minute. That's confusing for everybody and that's not good.
"What we want is clarity so people know what they're supposed to do and can follow the rules."
The city now appears on an updated list of tier two areas on the government's website after being added at about noon.
Rob Johnston, chief executive of Cumbria Chamber of Commerce, described the lack of clarity from the Department of Health as "about par for the course" and warned businesses would struggle with only "pretty poor" grants available to help them.