Video report by ITV News Correspondent Rebecca Barry
Claire Tomlinson-Blake, who cares for vulnerable adults in the East Riding of Yorkshire, sought to overturn a Court of Appeal ruling that carers are only entitled to minimum wage when they are required to be awake for work.
It means care workers like her who have to sleep at work in case they are needed overnight will not be entitled to the minimum wage for their entire shift.
"I feel gutted," she said. "I think that it's shameful, that is how I genuinely feel, it's shameful."
Ms Tomlinson-Blake, who is a support worker for Mencap, and John Shannon, a Surrey care home worker, brought the case to the highest UK court in February.
The long-awaited judgment is a sigh of relief for employers but will likely infuriate care workers who are often paid minimum wage for incredibly difficult jobs which have only been made harder by the pandemic.
Ms Tomlinson-Blake said: "It's the ultimate betrayal of people in the health and social care industry who are some of the most dedicated and hard working-staff in the country."
"To claim that they are not working when they are on shift is an ultimate betrayal," she added.
The landmark decision will save care providers from potentially “devastating” liabilities in back pay to their staff, estimated at £400 million, which could have seen many go out of business, lawyers said.
But the judgment was also described by trade union leaders as a missed opportunity, which will leave skilled staff being paid “poverty wages”.
Care workers who have to sleep overnight at their workplace on standby are often paid a flat fee of usually around £30.
But Ms Tomlinson-Blake said that they should get the minimum wage for the whole of their shift.
Ms Tomlinson-Blake said: “This case was never about the money. It was about the principle of treating staff fairly.
”Sleep-in shifts aren’t about just being on call – it’s work. Staff are constantly on guard to protect the most vulnerable in society. The sound of a cough in the night could mean someone’s in danger.
“It was nice to be clapped by the nation, but that was only temporary. The care workforce should be valued permanently. Respect for staff shows that the people we care for matter too.”
In the court’s written ruling, Lady Arden said that “sleep-in workers … are not doing time work for the purposes of the national minimum wage if they are not awake”.
She added: “The sleep-in worker who is merely present is treated as not working for the purpose of calculating the hours which are to be taken into account for national minimum wage purposes and the fact that he was required to be present during specified hours was insufficient to lead to the conclusion that he was working."
Trade union Unison said the ruling is a "blow" that will affect 200,000 workers.
Christina McAnea, General Secretary of Unison said: "They're not at home to tuck their children into bed or to make sure their elderly mother is settled for the night.
"They have to be on call to be able to get up to deal with anything that happens during the night and now this judgment comes out which basically says to them, the most you're going to get for working during the night is three or four pounds an hour if you're lucky."
Sue Harris, legal director of the trade union GMB, said: “GMB had already raised an eyebrow at the Court of Appeal decision – and we suspect many people will be surprised by today’s ruling.
“It essentially means if you are at your employer’s premises – not at your home – able to sleep, but know you may be disturbed at any time during that sleep, then those hours don’t count for the purposes of working time.
“Not many people would be able to sleep knowing they could be called to action at any moment.
“We have seen throughout the pandemic the wonderful work that carers do, they are the group in our society most likely to be on the minimum wage and that they are predominantly women and predominantly black, Asian, minority ethnic employees.
“This was a chance to address one of the reasons for the low pay of carers, it’s a shame it wasn’t seized upon.”
Edel Harris, chief executive of the Royal Mencap Society, said he understood many care workers would be upset by the result but said they contested the case because it would cost them £400 million.
He said in their view the cost of sleep-ins should be covered by the government as they are a statutory care service.
He said the current legislation covering “sleep-in” payments was “out of date and unfair”.
Matthew Wort, a partner at Anthony Collins Solicitors, which represented Care England, the body that represents independent care providers and intervened in the case, said: “The Supreme Court’s decision means UK care providers no longer face a potentially catastrophic financial outcome that could have jeopardised the care of thousands of people.
“This case was not about what care workers should be paid. Instead, it focused on the interpretation of national minimum wage regulations, with the law and previous government guidance making clear that carers are not working while asleep.
“Today’s judgment puts an end to many years of uncertainty. It should be seen as a line in the sand, with the focus now on ensuring changes are made in how workers are remunerated to ensure appropriate pay for time asleep.”
Mr Wort said the end of the case resolved a serious risk to the care sector "the long-term stability of the UK social care sector hangs in the balance."
He called on the central government to increase investment in social care.The government under both Theresa May and Boris Johnson have alluded to a review of the social care sector in the UK which is under enormous strain and is only set to get worse, but little progress has been made so far.