Consumer groups have warned that postal strikes could lead to delays in credit card holder’s bills and repayments.

One customer based organisation revealed that credit card balance statements and bills will be trapped among the 20million backlog of letters being held by Royal Mail.

The group said that the documents are being cleared because of widespread strikes across the postal network since July.

There are fears that banks will still carry on charging card holders for late repayments, so consumer advocates such as Richard Hammond, have urged providers to show more flexibility in the case of strikes.

Vince Cable, Treasury spokesman for the Liberal Democrats, added: “It is simply outrageous for banks to be landing thousands of customers with yet more charges for delays that aren't their fault.

“Banks must be more flexible over payment delays caused by postal strikes. They should pay back these punitive charges and end this practice immediately.”