(Bloomberg) -- Britain’s economy lost 220,000 working days to strikes in the first month of the year as unions targeted industrial action at the National Health Service.

The latest figure, published by the Office for National Statistics on Tuesday, means the UK lost 2.67 million days to labor disputes since June last year — the worst spell of strikes since 1990 when Margaret Thatcher was prime minister.

Still, January’s number was the lowest since September, down from 822,000 in the final month of 2022.

The drop is partly explained by postal workers who did not strike in January despite a long-running dispute with Royal Mail. The Communication Workers Union has tens of thousands of members at Royal Mail and secured a mandate last month for more strikes.

The number of days lost could rebound again in February, which began with a day of mass protest involving as many as half a million workers across multiple sectors.

Unions have been railing against pay offers that fall behind the UK’s rate of inflation with teachers, Tube drivers and civil servants walking out Wednesday to coincide with the unveiling of Chancellor of the Exchequer Jeremy Hunt’s latest Budget. Rallies and marches are planned in London, including outside Downing Street.

Teachers from the National Education Union, which has about 300,000 members, said they would not call off strikes until the government made “a reasonable offer.”

Read More: UK Labor Market Shows Signs of Easing With Weaker Pay Growth

Still, ministers have made some progress, with the Royal College of Nursing and ambulance unions suspending strikes and resuming pay talks. Disputes with junior doctors, however, were continuing Tuesday as part of a 72-hour walkout. 

©2023 Bloomberg L.P.