South Cambridgeshire Council, a local authority north of London, has been in a lengthy battle with members of the U.K.’s Conservative government over its four-day-week pilot, which has received fierce resistance since launching earlier this year.

Four-day week faces powerful foes

The council, run by the Liberal Democrat Party, began its trial in January when more than 700 staff moved to work 80% of their hours for full pay. The days of absence are staggered so its office hours remain the same as before the trial.

The group said it had moved to a four-day week because it was often unable to fill vacancies, leading to costly knock-on effects.

However, it has been met with strong opposition from the U.K.’s Department of Levelling Up, Housing and Communities (DLUHC), which argues the scheme doesn’t deliver Value for Money, an official measure used by the public sector to allocate taxpayer funds. 

In September, a defiant South Cambridgeshire said it would be proceeding with its trial through to March 2024 to understand its benefits to hiring and retaining employees. 

DLUHC Minister Lee Rowley had told the council to “end this experiment with taxpayer money” in July, before threatening legal action in September. The government submitted a “Best Value Notice” in November asking the council to submit data on the trial.

Now the U.K. government is exploring more aggressive options to curb South Cambridgeshire’s ambitions and prevent other local authorities from following suit.

In a Monday statement accompanying the announcement of a £4 billion ($5 billion) funding package for councils next year, the government said it was exploring the use of “financial levers” to force South Cambridgeshire to scrap the pilot.

“We are, and will, continue to work alongside councils to ensure quality and reliable services are provided to those who need and use them, while also keeping a weather eye on ensuring value for the taxpayer,” Minister for Local Government Simon Hoare said in a statement.

South Cambridgeshire standing firm

South Cambridgeshire maintains the trial isn’t costly to the government. It cited a study by the Bennett Institute for Public Policy, a think tank, which found that most of the council’s 16 areas of operations showed marked improvement during the first three months of the trial.

The council has since said that the policy has been a boon for recruitment and that since the trial began it has had much more success in hiring for positions regarded as “hard to fill.”

South Cambridgeshire Council didn’t immediately respond to Fortune’s request for comment. 

In a statement to Fortune, South Cambridgeshire leader Bridget Smith said her department was submitting 186 pieces of raw data to the department every week proving the efficacy of the trial. She said the U.K. government was simply ideologically opposed to a four-day week, “regardless of what the data is suggesting.”

“It’s very much the 21st-century way, which has been widely adopted in the private sector. If it works there, it needs to have a fair trial in the public sector,” Smith said.

A representative for the DLUHC didn’t immediately respond to Fortune’s request for comment.

Four-day workweeks are still in their nascent phase, often the result of pilot projects that largely indicate productivity is maintained or improved by the scheme, at least in desk-based sectors.

The Scottish government is in the process of rolling out a four-day workweek trial for its thousands of civil service employees. There are hopes the results of the trial will see Scotland’s private sector follow suit.

Luxury carmaker Lamborghini announced earlier in December that it was rolling out a four-day workweek for some of its production workers after reaching an agreement with its union.