Taxpayers face a legal bill of up to £400,000 after the SNP government’s ‘Orwellian’ policy of allowing trans women prisoners to be held alongside biological females was ruled ‘unlawful’.

Court of Session judge Lady Ross said it should be thrown out in a decision which campaigners said was a ‘victory’ for vulnerable women behind bars.

Feminist group For Women Scotland (FWS) had challenged the lawfulness of the Scottish Prison Service (SPS) stance on holding some trans women – who are biological men – in women’s prisons.

Its lawyer Aidan O’Neill argued it was ‘Orwellian’, comparing it to Animal Farm, George Orwell’s satire of Soviet Russia, claiming the practice amounted to ‘women good but men identifying as women better’.

Welcoming the judgment, Tory leader Kemi Badenoch said: ‘It’s time to draw a line under this. I do not understand why the SNP want to die on this hill of putting men in women’s prisons.

‘It’s extraordinary – there’s no common sense in the SNP, or with the Scottish Greens.’

She added: ‘We cannot have a situation like we had a few years ago, where rapists were put in women’s prisons.’

Lady Ross published her decision following the petition for judicial review brought by FWS, which challenged the Scottish Government’s policy on transgender prisoners.

FWS won a Supreme Court case last year which saw judges make clear the term ‘woman’ in the Equality Act refers to a biological female.

Now Lady Ross has ruled that while trans prisoners have rights under the European Convention on Human Rights, this does not extend to being accommodated in a prison for the opposite sex.

She also wrote: ‘Insofar as the prisons guidance allows SPS to accommodate trans prisoners in prisons for the opposite biological sex, it is in conflict with the requirement that prison accommodation be provided separately for men and women.

‘That constitutes a mis-statement of the law.’

She concluded that ‘in all the circumstances, the prisons guidance is unlawful’.

The case came amid the outcry over trans rapist Isla Bryson – formerly known as Adam Graham – who was initially sent to Cornton Vale women’s prison in Stirling after being found guilty in 2023 of raping two women.

Mr O’Neill argued the policy meant placing biological men convicted of serious offences alongside vulnerable women.

He said women prisoners were being ‘gaslit’ and used as ‘pawns’. Mr O’Neill also said: ‘It’s almost — if I can use Orwellian terms for it — Animal Farm-like. Women good. But men identifying as women better.

‘Or all women are equal, but men identifying as women are more equal than others.’

Welcoming the judgment, Susan Smith of FWS said: ‘We hope this will be the last time that we are forced to go to law to defend the rights of women. Ultimately, this is a victory for the very vulnerable women in the prison estate.’

It is believed that there are currently two trans women in the female prison estate.

Scottish Tory equalities spokesman Meghan Gallacher said: ‘It was outrageous that Swinney wasted taxpayers’ money fighting this case in court after the crystal-clear verdict from the Supreme Court last year.’

Gender-critical think-tank MurrayBlackburnMackenzie said: ‘That Scottish ministers defended this sexist and regressive policy for so long, and even went to court to do so, leaves a permanent stain on the reputation of every politician involved.’

An SPS spokesman said: ‘We are grateful to Lady Ross for her judgement, which we will carefully consider, at pace, along with the Scottish Government.’