A Royal Mail spokesperson has confirmed there had been “short-term pressures” on deliveries, but insisted the “vast majority” of letters send to the town have arrived as expected.
One Kilwinning man said the problems have grown over the last four months – with some letters arriving a month late.
He said: “Royal Mail postal services are running at four weeks behind at least. If you want your mail you have to visit the various sorting offices .
“Many people are waiting for hospital appointment letters which are not being received in time.”
A Royal Mail spokesperson said: “We know how important timely letter deliveries are and understand the frustration when delays occur.
“Deliveries have continued in Kilwinning, with the vast majority of letters arriving as expected, and the local delivery office was fully clear over the Christmas period.
“There have been some short-term pressures on certain routes, alongside poor weather earlier this month.
“Where delays have happened, deliveries have been managed to avoid prolonged gaps, and no areas have gone extended periods without receiving mail.”