ONE in five first class letters is failing to arrive on time, a survey has found.

We decided to put the hit-and-miss service to the test in the wake of recent local and national strikes.

Against the Royal Mail's own target of 91.5 per cent of first class mail arriving the next day, almost 80 per cent of post we sent arrived in the city on time.

We posted 60 letters on Saturday, January 19, and Monday, January 21, from across the country and within the city and county.

We even allowed the Royal Mail an extra day sorting - Sunday - to help get the post back to our Osney Mead base on time.

But only 47 arrived on time.

Post sent from outside the county was the least reliable, with only three-quarters of first class letters arriving on time.

However, reliability of first class letters sent from within Oxfordshire rose to 86 per cent.

Four letters posted within the city did not arrive when they should have done - a failure Royal Mail put down to disruption caused by "bad weather".

Yet post coming from as far away as Glasgow beat letters travelling just over a mile.

One letter posted from London did not arrive within a week.

Last night, Royal Mail said our survey was unscientific because it was too small.

Jane Askew posted mail from Warwick on Saturday and it arrived on Tuesday.

She said: "I made sure I posted it before the collection - it makes you wonder why you pay extra money for first class stamps."

Royal Mail spokesman Richard Hall said: "The last published figure of first class mail arriving next day stood at 78.4 per cent.

"This figure was severely affected by the local and national industrial action which took place over the summer."

However, strikes in Oxford ended in October and a normal service has been in place for more than eight weeks.

Mr Hall added: "It's difficult to rely on such a small sample, which is why Royal Mail spends more than £5m a year and sends over 100,000 test letters a month to provide a statistically representative picture of our performance."

Richard and Ying Groves run a luxury silk nightwear business from their home in Merrivale Square, Oxford.

Mr Groves said: "Thirty per cent of our business is posted from home and sent, depending on value, either by special delivery or recorded post.

"We have lost three or four items in the post recently.

"For one of our orders that never turned up, we had to send out a duplicate costing us £300, because we bear the cost of postage for our customers.

"All we were refunded was £34."

Anthony Harris, from Critchleys Accountants in Oxford, said: "Lately we have experienced a clear delay in post arriving, including a couple of instances when clients have told us they have sent key information for deadlines which then needs to be resent."

A spokesman for the mail service watchdog Postwatch added: "Customers should expect at least 93 per cent of first class mail to arrive next day. It is disappointing only 80 per cent of letters posted arrived on time."

Anna Beaumont posted her letter from Sutton Park in Hull and it took two days to arrive - twice the time it should have done.

She said: "I usually send important post first class. It's interesting to think it doesn't always guarantee next day delivery."