Following an invitation from the arbitration body, the union – which represents postal workers – will now be attempting to resolve the ongoing dispute over pay and changes to working practices.

But its members are still on strike as part of a wave of declared days of strike action.

The following statement has been agreed by all parties: “Following an invitation from ACAS, Royal Mail and CWU have agreed to jointly engage with ACAS facilitation in an attempt to resolve the current disputes on pay and change.

“There is a commitment on both sides to reach a resolution, however we all acknowledge there are significant difficulties to overcome.

“An opening session will now take place on Tuesday 25 October with the objective to reach an agreed approach for further facilitated talks.”

CWU general secretary Dave Ward said: “We welcome the mutual agreement to attend ACAS discussions as a positive development, but at this stage, it is not a greatly significant one either.

“This is why the union has not chosen to suspend or call off scheduled strike action.

“Our members are fighting against a bullying management set on stripping their pay, trashing their job security and side-lining their union – it will take more than ACAS talks to hold them back.”

He added: “Until the employer reins in its relentless attacks on employees, the strikes will continue to take place.

“Postal workers are completely united in their determination to secure the dignity and respect they deserve. We won’t be backing down until we get just that.”

CWU acting deputy general secretary Andy Furey added: “As each week goes by, postal workers are becoming angrier and angrier at their mistreatment.

“Picket lines are growing in numbers and the resolve of all CWU members is hardening – people are not simply accepting what is being done to them by management.

“Our posties will keep on fighting, and we urge the public to get behind them.”

Amid ongoing disruption to delivery schedules caused by the strikes, that began at the end of September, and are set to continue throughout October, November and December, Royal Mail has brought forward a swathe of price increases originally slated for next year.