Some people admit to opening wrongly delivered letters

Almost 500,000 letters are lost in Northern Ireland every year, according to a consumer group.

Postwatch said people had missed hospital appointments and failed to receive benefits on time because letters were delivered to the wrong address.

It said changes in postmen or carelessness in the sorting office caused some of the problems.

But Postwatch said Royal Mail was not solely to blame and urged people to properly address their mail.

The organisation's Northern Ireland chairman, John Stringer, said although the lost letters figure was very high, it was lower than previous years.

"There's no doubt that of those half a million, many of those are causing great problems in terms of people not getting hospital appointments, not getting information about attending for interviews, not getting examination results," he told BBC News Online.

"A whole catalogue of things that have happened that inconvenience people terribly."

He said one of the worst cases of mis-delivery in Northern Ireland was in Newtownabbey, County Antrim.

People living in two neighbouring blocks of flats, Woodland House and Beechwood House, have been receiving each other's mail in error for almost a year.

David Chambers, secretary of Beechland Residents' Association, said many of the residents were elderly and relied on their post to receive important financial and medical letters.

He said: "Our main concern is that if letters are mis-delivered to another flat residents may not get important mail, such as benefits or hospital appointments, days - or even weeks - later than expected, particularly if the other flat is empty."

Some people simply post a wrongly addressed letter again

He said mail had been hand-delivered where residents knew the intended recipient, but in other cases it was left it in a communal lobby.

Mr Chambers added: "When you consider that some mail contains cheque cards, benefits, or other important financial information, to think it might be lying around for anyone to pick up is a real concern."

A spokeswoman for Royal Mail said it would be meeting the residents' association to discuss the extent of the problem "with a view to addressing the problem".

Nationally, 14.4m letters are lost in the UK every year and of these 60% are just put through the wrong letter box.

According to Postwatch, only 10% of customers complain to Royal Mail - and even those who posted a wrongly addressed letter again, or delivered it themselves, took up to a week to do so.

The group is publishing a pack urging customers to let Royal Mail know about mistakes.

Mr Stringer said: "The problem happens more in towns and cities than it does in rural areas, this is because usually in rural areas the postmen know their rounds really well.

"In towns and cities you get changes in postmen, you get casual postmen, or those not properly trained."

He added: "Thousands of letters every month are accidentally put through the wrong letterbox and are never passed on to the correct address and that letter sitting in your home could mean a great deal to the person it is addressed to.

"Our message to customers is that if Royal Mail do not know about the problem they cannot fix it."

Michael Kennedy of Royal Mail in Northern Ireland said one of the main reasons why letters went to the wrong addresses was badly addressed mail or postmen making a mistake.

Campaign pack

He said as a result the company could face penalties of up to �50m in fines this year across the UK.

But he pointed out that Royal Mail fully supported the Postwatch initiative.

"There will be compensation for any customers where we have significantly delayed mail," he said.

"For private customers it will be 12 times the value of the stamp for delays of four days and over, but significant delays up to �5 or �10.

"Over the past two years, we have halved the number of missed deliveries, that's through working with major customers to improve their addressing and also training our postmen to avoid misdelivering mail."

Customers can get a copy of the Postwatch campaign pack by logging on to www.postwatch.co.uk/misdelivery or by telephoning the helpline on 08456 013265.