Alexis Quinn, pictured, was due to take the landmark case on human rights grounds

The action is expected to proceed quickly following the policy being finalised in the Budget next Wednesday (file image)

But this week, Miss Quinn announced that Rochester College in Kent, where her 12-year-old daughter Addison is a pupil, has stepped in ‘unexpectedly’ to offer a ‘generous scholarship’ to enable her to remain at the school.

She has been replaced in the action by two new claimants – who are currently anonymous.

But it is feared the switch at such short notice may harm the case.

Charity worker Miss Quinn told supporters she was ‘both relieved and disappointed’ by the last-minute offer from the school.

She said: ‘This is both an unexpected and incredibly supportive act.

‘I am relieved because Addison can stay at the school she loves, and disappointed that I am now no longer a viable candidate to challenge the Government’s ill thought-out and harmful VAT policy because the scholarship means Addison’s school place is now affordable for me, undermining my case.’

The two new claimants are single parents of children with special needs, who say they have ‘limited incomes’ but a private education ‘has proved vital for their children’s welfare’.

The action is expected to proceed quickly following the policy being finalised in the Budget next Wednesday.

One of the parents, from Somerset, who runs a childcare business, says they spend ‘every last penny on paying the private school fees’ but the additional burden, even though the school has said it will restrict this to 10 per cent, will make fees unaffordable and it ‘would be traumatic’ for their child move school.

They say they moved their eight-year-old autistic boy, who was previously in care, to a small prep school because he could not cope in his mainstream school where he even had to wear ‘ear defenders’ in class because of sensory overload.

The action, due to start within weeks at the Royal Courts of Justice, was to be launched as a test case

His former school was judged by Ofsted and the Care Quality Commission to have ‘poor outcomes for children and young people with SEND’ (special educational needs and disability).

The Government has previously said that only children with education, health and care plans (EHCPs) which state that they need a council-funded place in a private school for specialist support will not be impacted by VAT.

Meanwhile, there are more than 100,000 children without EHCPs in independent schools whose education could be disrupted, campaigners against the tax have warned.

EHCPs are often hard to obtain even for those in genuine need, and the process takes a long time, leading some parents to just go private.

Paul Conrathe, from Sinclairslaw, who are acting in the case, has previously said vulnerable children will be ‘discriminated against because the state doesn’t have the provision that’s necessary to meet their needs’.

His firm sent a pre-action letter which puts the government on notice of the intention to issue proceedings in the High Court to Chancellor Rachel Reeves.

The Government has claimed its policy will raise £1.5 billion a year to fund new teachers buts its sums, which are based on only three to seven per cent of children quitting private schools, have been widely disputed.