Unions say the single daily delivery service has caused problems

Alex Skinner, secretary of the Communication Workers Union in Edinburgh, said quality of service had suffered due to "unrealistic" savings.

He said Royal Mail chief executive Adam Crozier did not understand what was required to run a public company.

Mr Crozier said there was "real evidence" its service was improving.

Figures published by the Royal Mail on Tuesday reveal it was now delivering about 92% of its first class mail the next day - below its target of 92.5%.

In Glasgow, 90% of first class letters were delivered the next day in May - last month that figure had slumped to 81%.

The quality of service to the public is suffering Alex Skinner PWU

Six of Scotland's postcode areas used to be in the UK's top 20, but only Kilmarnock, Paisley and Dundee have made the grade.

Mr Skinner said postal workers were facing increasing pressure in their jobs and claimed the impact of the Single Daily Delivery (SDD) service had been "horrendous".

Speaking on BBC Radio's Good Morning Scotland programme, he said postal workers were becoming disillusioned.

He said: "There are teething problems with the SDD system at the moment.

WORST DELIVERY AREAS Glasgow - 80% First Class post on time Lerwick - 81.4% Swansea - 81.9% Kirkwall - 83.5% South east London - 85% North London - 85.3% Liverpool -85.9% The Hebrides - 85.9% Peterborough - 86% Performance figures in full (Source: Royal Mail)

"We believe too much emphasis has been placed on budget cuts and not enough on the quality of service itself.

"People are the tools of the job and at the moment we are facing difficulties keeping postmen in the job."

Mr Skinner said nightshifts in some postal offices in Scotland had been cancelled.

"So the postmen who were used to getting their mail set up for them in the morning, now have to do it themselves before going out," he said.

"The quality of service to the public is suffering. People in the post offices want out because of the pressures."

Making progress

Mr Skinner said the Royal Mail's chief executive "carried 100% responsibility" for the performance levels and targets.

"Adam Crozier came into this industry from the Football Association, where he didn't do such a great job, and I don't believe he understands the workings of a public company like the Post Office and what it means to the public," he said.

Royal Mail said that while it missed all of its targets during the three months to June, it was now hitting four of its 15 targets, according to preliminary figures for August.

Mr Crozier said the organisation was now making progress, adding that 95% of the operational changes - such as scrapping the second post - had now been made.