Claims under sections 19 and 20 of the Equality Act 2010 require that a provision, criterion or practice place (or in s.19 would place if applied) an individual with a protected characteristic at a substantial (in the case of section 20) or a particular (in the case of section 19) disadvantage.
In Edie & 15 Ors v HCL Insurance BPO Services Ltd  UKEAT 0152_14_0502 the Employment Tribunal asked the question as to whether the imposition of new – and detrimental – contractual terms could amount to a PCP with reference to section 19(1) of the 2010 Act. I don’t see why this would not equally apply to the PCP in section 20(3) of the Act.
In many ways this is a commonsense decision but the clear authority that a change of contract situation does not just raise prospects of a common law/constructive dismissal remedy but also (especially) protection on indirect discrimination grounds is a welcome one. This is because it gives a more tangible protection to workers than the theoretical option of constructive dismissal arguments (if you’re on the breadline walking away from an income even if a breach is grievous and fundamental it is not often a realistic option and this gives employers a license impose inequitable changes).
Certainly in my experience members in the PCS Union are seeing a raft of changes in the workplace, changes that in my view are likely to amount to contractual variations. Many of these do place particular groups (expecially on age and disability grounds) at a disadvantage. So, for example, changes to a contractual grievance procedure that applies to all employees and make it harder to have grievances heard may still place disabled employees at a disadvantage if disabled staff are five times more likely to submit a grievance than non-disabled staff.
This doesn’t change much but at least it makes it a bit easier to force employers to objectively justify their discriminatory conduct since it is less easy to evade the issue by denying contract changes are a PCP.