Ireland's labour tribunal ordered social media firm X, previously Twitter, to pay a £470,000 (550,000 euro) fine for the unfair dismissal of a former executive after he failed to reply to an email following Elon Musk's takeover.

The Workplace Relations Commission (WRC), which rules on employment disputes in Ireland, ordered X to pay Gary Rooney the amount on Monday, with the Irish Times reporting it was the largest sum for unfair dismissal ordered by the body.

Rooney, an ex-senior executive at Twitter's Europe headquarters in Ireland, was told he had resigned when he did not respond to an email sent by Musk after he bought Twitter at the end of 2022.

The email set out a vision for a "Twitter 2.0" calling for employees to be "hardcore", with Musk writing "If you are sure that you want to be part of the new Twitter, please click yes on the link below".

Those who did failed to click "yes" were told in the email that they would receive three months of severance pay.

Rooney had worked at Twitter for nine years before he was considered as having resigned in November 2022.

However, Rooney's decision not to click "yes" in the email did not constitute a resignation, WRC official Michael MacNamee concluded in a decision reported by the Irish Times.

The full ruling will be made public at the end of August.