Whistleblowing claim struck out: relitigating the same disclosure

This case shows the limits of bringing repeated claims based on the same underlying facts. The former engineer, who had 15 years' service, alleged he made a protected disclosure to his MP in November 2017. A previous tribunal had already decided that this communication was not a protected disclosure, and all claims in that case failed.

Despite that, the claimant issued further proceedings relying on the same disclosure. The tribunal applied the principle of res judicata – meaning 'a matter already judged' – to strike out the whistleblowing detriment claims against Transport for London and two individual employees. The individuals were considered to have a sufficient identity of interest with the employer, so the earlier decision bound them too.

The remaining claims for victimisation and indirect disability discrimination were later struck out as an abuse of process. The claimant then withdrew all remaining claims at 5:07pm the day before the final hearing, leading to a costs order of £2,940 for the unreasonable late withdrawal.

What Transport for London did right

Transport for London successfully argued that the core issue – whether a protected disclosure had been made – was already decided. They also demonstrated that the individual respondents were so closely connected to the employer that the same principle applied.

What the claimant could have done differently

Rather than relitigating the same disclosure, the claimant could have focused on any genuinely new disclosures or different legal claims. Withdrawing at the last minute without explanation was a costly mistake.

Why this matters

This case is a reminder that employment tribunals will not allow claimants to have a 'second bite at the cherry' on issues already decided. It also highlights the risk of costs when claims are withdrawn late, especially for unrepresented claimants who may not fully understand the procedural rules.