Keir Starmer has hit out at claims that the government suppressed furlough funding for sick workers self-isolating at the height of the Covid pandemic.

The Labour leader waded into the row after it emerged that senior civil servants had complained that the Treasury was worried about publicising a relatively unknown provision in the furlough rules that allows temporary payments for staff forced to quarantine.

The Politico.eu website said it had seen emails, dated from January and February this year, showing that officials had complained about the failure to make employers and staff aware of the guidance.

“Furlough can be used to cover self-isolation, but [the Treasury] are reluctant to say this explicitly in guidance because it could lead to employees being furloughed who do not need to be,” one email read. “This is a live issue being worked through.”

One senior official explained in their complaint: “Incentive payments are too low to incentivise employees to take tests due to risk of loss of income.”

Both Downing Street and the Treasury insisted that the guidance was clear on the government’s own website that the furlough scheme had never been intended to be used as a substitute for statutory sick pay.

But Labour said the revelations were “shameful and reckless”, with Starmer adding he was “really concerned” about any suggestion of restricting cash help for home quarantine.

“One of the big issues for the 14 months or so we have been in the pandemic has been whether people feel that they can afford to self-isolate,” he told reporters during a visit to Airbus in Bristol.

“Self-isolation is a huge tool in the armoury when it comes to defeating the pandemic, but too many people felt that they couldn’t afford to self-isolate.

“We have been saying this for a year or more, so the idea now that this has been suppressed I think is so wrong in terms of how we fight this pandemic.”

Shadow Treasury minister Bridget Phillipson added: “It is shameful and reckless that the Chancellor ignored professional advice and put countless people and workplaces at unnecessary risk when he had the opportunity to help.”

The government guidance for firms makes clear that short-term illness or isolation “should not be a consideration when deciding if you should furlough an employee”.

But it adds: “If, however, employers want to furlough employees for business reasons and they are currently off sick, they are eligible to do so, as with other employees. In these cases, the employee should no longer receive sick pay and would be classified as a furloughed employee.”

Government sources said that the reason for the rules was that HM Revenue & Customs would have no mechanism or way of identifying those being furloughed for short term sickness, and it could open the whole scheme to fraud risk.

The prime minister’s official spokesperson said: “The guidance on Gov.uk sets out that the furlough scheme is not intended for short-term absences from work due to sickness and self-isolation should not be a consideration when a business is deciding if a business should furlough an employee.”

A Treasury spokesperson added: “It has always been clear that the purpose of the furlough scheme is to support jobs – we’ve been upfront about that from the start.

“We have a specific support package in place for those self-isolating due to coronavirus, including £500 one off payments for those on low incomes.

“If an employer wants to furlough an employee for business reasons and they are currently off sick then they are eligible to do so as with other employees. This has been set out in guidance since April last year.”

Separately, Downing Street tried to play down reports that ministers would legislate to allow a legal right to work from home because of the pandemic.

“We’ve asked people to work from home where they can during the pandemic but there are no plans to make this permanent or introduce a legal right to work from home,” the PM’s spokesperson said.

“There’s no plans to make working from home permanent or introduce a legal right to work from home.”

But he added the government was committed in its manifesto to a possible default right to flexible working. “What we’re consulting on is making flexible working a default option, unless employers have good reasons not to.”

He defined flexible working as “a range of working arrangements around time, place and hours of work including part-time working, flexi-time or compressed hours” but not necessarily working from home.