Royal Bank of Scotland, the nationalised bank, has sent threatening letters to homeowners saying that their homes will be repossessed if they fail to repay their entire mortgage within 30 days.

NatWest, which is owned by RBS, demanded that Peter Addyman, a married pharmacist from Hastings, East Sussex, repay his £226,000 home loan – although he says he has never missed a payment.

It has refused to give an explanation for its decision, even to the Addymans’ MP. The actions have outraged consumer groups, who say the bank has an obligation to treat customers fairly after accepting £20 billion in a government bailout.

Michael Foster, the Hastings and Rye MP, said: “There’s no doubt they’ve raised the cost of mortgages since this family was granted one.

“I’ve written twice to NatWest but have received a wall of silence. They won’t tell this family what they’ve done wrong. If it comes to it, I think the court would exercise its discretion not to order repossession in this case.”

In another case, Royal Bank of Scotland wrote to a homeowner who had missed just one payment on his mortgage, ordering repayment within 30 days. Correspondence sent by the bank and seen by The Sunday Times uses identical words to the letter sent to the Addymans. Again, it is understood RBS refused to give a detailed explanation for their decision.

The Addymans insist they are not in arrears, and have not missed any payments since taking out the interest-only tracker mortgage nine months ago. They have received default notices for credit card debts in the past, and they have a second mortgage on the property. However, the additional mortgage and debts occurred before RBS signed the mortgage in March 2008.

NatWest first wrote to the Addymans in September and said: “We . . . will no longer provide these facilities for you, which includes mortgage arrangements. The Bank requires a copy of a new mortgage offer within 30 days from the date of this correspondence to avoid further recovery action.”

A spokesman for Which?, the consumer group, said: “It’s not good enough. This flies in the face of the bank’s and the government’s rhetoric on reposessing homeowners” A spokeswoman for RBS said there were “exceptional circumstances” in the Addymans’ case, but did not explain what they might be. She said: “This is not a move that we take lightly. This case has absolutely nothing to do with our processes for managing customers who are experiencing difficulties.”

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