WhatsApp messages are increasingly being used as evidence during bitter employment tribunals, with companies warned they could be at risk of having to pay out hefty fines if they aren’t monitored.

The number of tribunals that have referenced the messaging app has almost tripled since 2019, from 150 to 427 hearings in 2023, according to figures from the HM Courts and Tribunals Service.

The data was obtained by law firm Nockolds as employers were warned misuse of the platform could see them having to pay out thousands of pounds in compensation.

NatWest this month announced it was banning staff from using WhatsApp, Skype and Facebook in an effort to stick to rules over workers’ use of unauthorised electric messaging as well as to avoid fines.

Lawyers have warned employees could be sacked for sending derogatory private messages about their managers or colleagues.

Making jibes about someone’s age, 𝑠e𝑥, 𝑠e𝑥ual orientation, gender reassignment, or religious beliefs could also land staff in hot water.

Jokes about someone’s appearance are also ‘big risks’ as they could be seen as offensive.

Ian Jones, the director and principal solicitor at Spencer Shaw, told The Telegraph: ‘If there is a sufficient work connection to the WhatsApp group, almost inevitable if the members are a group of work colleagues exclusively, then any wrongdoing by employee – harassing comments, discriminatory behaviour (even if unintended), bullying, reference to 𝑠e𝑥 or 𝑠e𝑥ual issues – will mean that the employee may be liable to disciplinary or even legal action.’

Dawn Dickson, a partner at Anderson Strathern, added that it didn’t matter what the sender intended but how the message is perceived and the impact it had.

‘If this kind of behaviour continues unchecked, it could lead to harassment claims or even constructive dismissal, which can be expensive for employers,’ she warned.

A judge ruled in October 2023 that excluding colleagues from WhatsApp group chats can be discrimination.

Employment Judge Sarah George said bosses need to have a good justification for failing to include staff in chat groups – even if they are absent.

Being left out of messages while workmates are included can be viewed as an ‘unfavourable act’, she added at an employment tribunal hearing in Watford.

Her ruling came in the case of Mark Brosnan, 60, who was awarded compensation after claiming he was discriminated against while suffering from a bad back.

One of Mr Brosnan’s complaints was that he was left out of a work group chat to ‘communicate important safety information’ because he was off sick with the recurring injury. And a tribunal agreed that being left out was unjustified.

He was awarded £134,411 in compensation for the company’s ‘completely unreasonable’ conduct in proceedings where they did ‘literally nothing’ to aid his ability to return to work.

This included £15,000 in injury to feelings, £7,000 personal injury and over £25,000 in loss of future earnings.