Three train operators facing collective proceedings for allegedly overcharging passengers have been accused of trying to ‘strangle the emerging regime at birth’ at the Court of Appeal.

Consumer champion Justin Gutmann, formerly of Citizens Advice, is bringing two opt-out claims valued at around £93m against the operators of the south-western and south-eastern rail franchises on behalf of around three million people.

First MTR and Stagecoach – which operated the south-western franchise at different times – and London & South Eastern Railway are said to have abused their dominant positions by failing to make so-called ‘boundary fares’ sufficiently available for travelcard holders, which is denied.

The Competition Appeal Tribunal granted a collective proceedings order (CPO) last year for just the third time since the introduction of collective proceedings, after CPOs were made in a mammoth £14bn claim against Mastercard and a £590m action against telecoms giant BT.

But the three operators are appealing against the granting of a CPO, with LSER’s lawyers contending that the claims are an attempt to circumvent the need for each claimant to have a proper cause of action by pursuing an aggregate damages claim, leading to a ‘clear risk of overcompensation’.

Paul Harris QC said in written submissions: ‘What was required to be demonstrated at the CPO stage was an administratively feasible and fair methodology for “winnowing out” uninjured class members.’ He added: ‘If, at the CPO stage, no basis in fact is advanced for winnowing out uninjured class members … prior to determination at trial, then (unless remedied at trial) there will necessarily be an over-estimate of the aggregate damages suffered by the class.’

However, Gutmann’s lawyers told the court that the effect of the appellants’ arguments would be to kill off the collective proceedings regime introduced by the Consumer Rights Act 2015. ‘They are trying to make the new regime unworkable,’ Philip Moser QC said, ‘unworkable for perhaps the principle purpose for which it was created, namely vindicating consumers’ rights against dominant corporation behaviour of this kind.’

He added: ‘Over-inclusivity does not equal overcompensation … a potentially over-inclusive class may be certified in an aggregate damages case and a number of things can happen. It can be refined or the damages can if necessary be reduced by conservative assumptions, if necessary, at trial.’

Moser said it was ‘self-evidently impracticable’ for the operators to ‘challenge each claimants’ case individually’ to discover if they suffered loss and, if so, to what extent, adding: ‘This is in reality an attempt to strangle the emerging regime at birth as regards consumer-type claims.’

The hearing before Sir Julian Flaux, Lord Justice Green and Lady Justice Whipple is due to conclude today.