Royal Mail is investigating allegations that a postal worker claimed to have “dumped” Reform UK campaign leaflets in a bin ahead of Thursday’s local elections.

A post on a Facebook group for Royal Mail staff said: “My DO had reform party’s D2D today. I dumped them all in a bin. They can sack me! Idgaf!”

“DO” is an acronym for delivery office, “D2D” for door-to-door or unaddressed advertising mail, and “IDGAF” means “I don’t give a fuck”.

The message was shared to a private 30,000-member Facebook group called Royal Mail Chat. It is unknown which part of the UK it involved.

A Reform UK legal representative wrote a letter of complaint to Alistair Cochrane, the chief executive of Royal Mail, which said the screenshot was circulated on Saturday.

Royal Mail said it “plays a crucial role in elections” and “we take our responsibility very seriously and do not tolerate the deliberate non-delivery of mail”.

It added: “We are investigating this allegation and remain committed to impartial delivery for all candidates.”

The Reform leader, Nigel Farage, said on X: “It is right that @RoyalMail have launched a full investigation into this allegation.

“If found to be true, it would be very disturbing and an attack on the democratic process itself.”

Reform has demanded an “immediate and thorough internal investigation” within three days of its letter, dated Saturday, and a full written explanation in addition to any compensation measures “Royal Mail proposes to offer Reform UK for the loss and disruption caused by this incident”.

The party is also seeking confirmation that appropriate disciplinary action “up to and including summary dismissal” has or will be taken “against any employee found to have participated in or condoned the destruction of the materials”.

It called for written assurances that future Reform campaign deliveries will be “prioritised, properly monitored, and safeguarded against any recurrence”.

The legal representative said of the Facebook post: “This admission provides clear prima facie evidence of the deliberate destruction or non-delivery of Reform UK’s door-to-door campaign materials that had been entrusted to Royal Mail.

“Such conduct constitutes a wilful breach of Royal Mail’s statutory and contractual obligations to deliver mail and literature impartially and efficiently.

“It also undermines the democratic process and Reform UK’s lawful right to engage in political campaigning.”

The Facebook group is open to Royal Mail employees and partners, as well as members of the Communication Workers Union, a trade union covering postal delivery workers.