(Bloomberg) -- The economy lost nearly 2.5 million working days to strikes last year as Britain suffered its most severe industrial action since Margaret Thatcher was in power.

The Office for National Statistics said Tuesday that 843,000 working days were lost due to labor disputes in December, making it the worst month in more than a decade. 

That took the total for June to the end of the year to 2,472,000 days lost. The last time it was worse was 1989-90, toward the end of Thatcher’s time as prime minister. Up until June, the ONS had temporarily stopped measuring the data due to Covid.

Unions are railing against pay offers that fall behind the UK’s rate of inflation.

Protests have escalated this year with major walkouts held by hundreds of thousands of rail staff, civil servants, teachers and workers in the National Health Service and elsewhere in the public sector. On Feb. 1 as many as half a million went on strike together.

“The wave of industrial action across the UK isn’t going away,” said Sharon Graham, general secretary of the union Unite. Responding to the ONS data, she said workers “have no option but to fight for better wages.”

The RMT union rejected another pay offer for rail workers at the end of last week, raising the prospect of more train strikes. 

Nurses’ strikes extending over two consecutive days could become more common, according to reports.

“A continuous 48-hour strike that includes staff from emergency departments, intensive care units and cancer care services would likely have the biggest impact on patients we’ve seen,” Saffron Cordery, deputy chief executive at NHS Providers, said in an emailed statement at the weekend.

Junior doctors are expected to vote in their thousands in support of strikes with a ballot closing next week and industrial action due early March. More ambulance drivers in southern England and Yorkshire also joined the wider NHS dispute over the weekend and will take part in upcoming strikes.

Read More: City of London Workers Threaten to Strike Over Pay

Prime Minister Rishi Sunak’s government has refused to lift public sector remuneration for the current fiscal year beyond levels proposed by pay review bodies that it insists are independent. Unions say they will keep fighting, with rail workers and Royal Mail staff being re-balloted for the right to hold strikes into the summer and possibly beyond.

Unite general secretary Graham said Tuesday that Sunak resembled “the captain of the Titanic” after he reshuffled his government in the face of mass protests and weak poll ratings.

Private sector wages have outpaced the public sector in the last two years, but the rate of increase in government roles has jumped to 4.2% according to official data released Tuesday — the fastest since 2006. Climbing salaries are raising concern that inflation could remain persistently high.

Read More: BOE Warns UK Public Sector Pay Raises May Spur Inflation

While the strikes may not have had a huge effect on GDP, shops, bars and restaurants in city centers have suffered from disruption on the public transport system. Footfall at shopping areas near central London offices was up more than 36% year-on-year last week as commuters returned following train strikes at the start of the month, according to data company Springboard. A year earlier, many Britons were still working from home due to the omicron variant.

--With assistance from Andrew Atkinson and Lisa Pham.

(Updates with comments from Unite general secretary from sixth paragraph.)

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