The SNP has called on the UK Government to order an investigation into Royal Mail after new figures showed "appalling" postal service in Scotland's islands.
Research commissioned by the SNP found stark differences between delivery performance in Scotland's island communities and other parts of the UK.
According to the figures, only 31% of first-class mail in Shetland was delivered within one working day in the latest year. In the Outer Hebrides, Orkney and Caithness, the figure was 54%, while Argyll and parts of the Western Isles recorded 61%.
By comparison, many postcodes in south London achieved on-time delivery rates of 75% or higher.
The findings come despite Royal Mail's universal service obligation, which requires it to provide the same level of service across the UK regardless of location.
The research also found Royal Mail has met its target of delivering 93% of first-class mail within one working day just three times since the company was privatised, and not since 2016/17.
During the same period, the price of a first-class stamp rose from 64p in 2016 to £1.80 in 2026.
The SNP said the figures showed rural Scotland was being failed and called on the UK Government to press communications regulator Ofcom to investigate Royal Mail's performance.
Highlands and Islands MSP Jenni Minto said: “Year on year the service provided by the Royal Mail continues to diminish – the damage done to this vital service impacts those in rural communities hardest.
“The decision to sell off the Royal Mail by Westminster was short-sighted and neglectful. It is no a surprise it’s been over a decade since they last met their targets."
She went on: "What is most concerning is that parts of Scotland, particularly the Highlands and Islands, have seen the level of service they receive drop far below that of Southern England.
"It is time for the UK Labour government to take their heads out of the sand and press Ofcom into finally holding the Royal Mail to account for this unacceptable level of service.”
A spokesperson for the Department for Business and Trade said: "Ministers have been clear with Royal Mail that services haven’t met the expectations of customers for quite some time now. It is particularly important that their service to rural and island communities improves.
“We expect Ofcom, as the independent regulator of postal services, will take an active interest in their performance across the country."