MP for Westmorland and Lonsdale Tim Farron is calling on Royal Mail bosses to pay postal workers overtime or risk cards and presents being left undelivered this Christmas.

It comes as regulator Ofcom ended an investigation into Royal Mail’s performance and found that the company had failed to hit some of its annual delivery targets.

Just 82 per cent of first-class mail was delivered within one working day, below a target of 93 per cent, while 95.6 per cent of second-class post was delivered within three working days, against a target of 98.5 per cent.

Ofcom said 94.29 per cent of delivery routes were completed each day a delivery was required – against the target of 99.9 per cent.

Mr Farron is calling on Royal Mail to come to an agreement with the Communications Workers Union to stop any further strike action.

The CWU has formally notified Royal Mail it is calling on its members who collect, sort and deliver parcels and letters to take national strike action.

Workers are set to walk out on the following dates: December 9, December 11, December 14, December 15, December 23 and December 24.

He said: "This is an absolutely appalling situation which could threaten to ruin Christmas for many people.

"Meanwhile the situation is only set to get worse with Royal Mail's failure to settle the ongoing dispute with the unions over pay and conditions leading to more strike action.

"It's clear that Royal Mail’s mismanagement means that they lack capacity to do the basics, which should persuade them that their dreadful plans to close Sedbergh Delivery Office would make things even worse.

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"Royal Mail must do a U-turn and be prepared to pay their staff overtime so that cards, letters, and parcels can be delivered on time.

"This isn't the fault of our postal workers - they are simply not being allowed to provide the service they desperately want to provide."

Meanwhile, there are reports in the national media that postal workers fear that letters posted now may not arrive in time for Christmas due to the backlog.

Lindsey Fussell, Ofcom's group director for networks and communications, said: "We're concerned by Royal Mail’s performance so far this year, which is falling well short of where it should be. 

"It must do everything it can to bring service levels back up and we'll be keeping a close eye on it throughout the year."

Simon Thompson, Royal Mail’s chief executive, said: “Talks have lasted for seven months and we have made numerous improvements and two pay offers.”