A MYSTERY shopping investigation revealed some "basic errors" at post offices, including advice on whether to send items second class.

Citizens Advice said that although 75 per cent of shoppers were satisfied with the level of service at local branches, a number of "inconsistencies" were found.

Staff correctly recommended that an item should be posted second class in only 39 per cent of cases, while almost one in 10 shoppers could not withdraw the amount of money they wanted.

The new model of local post offices, often sited inside shops, has improved opening hours, but four per cent of the mystery shoppers found the store was closed when it should have been open.

After 457 visits, the shoppers said queue times were "broadly good", being served immediately in 60 per cent of cases.

The report said that in 97 per cent of cases, accessibility was good or had been recently improved, although it added: "In an unacceptable minority of cases, there are persistent problems with access into and around the premises for elderly or disabled consumers."

Gillian Guy, chief executive of Citizens Advice, said: "Local post offices are crucial to consumers and businesses so these changes are absolutely vital.

"They have the potential to ensure the sustainability of the network and protect its role at the heart of communities.

"While the principles behind the reforms are right, our investigation has uncovered some inconsistencies with service delivery that quickly need to be put right.

"Post Office Ltd should urgently iron out these problems to ensure the new service works effectively for all consumers."

Post Office spokesman Mark Davies said: "Our modernisation programme is delivering longer opening hours, greater accessibility for customers and a branch network sustainable for the future.

"These mystery shopper visits to a number of branches at the start of the year show waiting times coming down, with 60 per cent of customers served instantly in local branches, and the vast majority of mystery shoppers being satisfied with staff knowledge on the scenarios tested, as well as with the overall experience of their visit.

"This tallies with our ongoing research based on customer experiences which consistently shows over 95 per cent customer satisfaction with the Post Office Local model.

"There is always room for improvement and we will consider as a business what further steps we can take to improve service for customers, but the findings of this research, if not the narrative which accompanies it, shows positive steps forward in one of the largest transformation programmes in Europe."