By bizn_fun 
Speaking to BBC Breakfast, Liam Byrne, chair of the Business and Trade Committee, said he had seen the comments made by viewers and wanted reassurance from the company that things would improve.
“Is there any truth to the stories that they are prioritising parcels instead of letters?
“Is there any truth that they’re batching up letters in big piles before they embark on deliveries to houses?
“We’re going to need to see a plan on the table now to reassure us that this service is going to be stood back up to what the nation expects,” he said.
In the letter to Royal Mail, the committee raised “significant concerns” about reports of “failures in service” that go beyond normal seasonal pressures.
It has demanded “categorical assurance” that parcels are not being prioritised over letters, and has given the company until 2 March to provide commitments to address the “chaos”.
Royal Mail told the BBC it only prioritised parcels when it was necessary to do so in order to clear bulky items from sorting offices for health and safety reasons. It said it was normal for people to receive a number of items at the same time, creating a perception of so-called “batching”.
The regulator, Ofcom, has fined Royal Mail £37m in recent years for poor performance delivering letters.
Following the publication of the letter from MPs, Ofcom told the BBC it expected to see meaningful change from Royal Mail soon and that, if that does not happen, “fines are likely to continue”.