The Post Office network could head the same way as Woolworths unless urgent action is taken to stop it declining, a Sussex study has claimed.

Its authors said there was an undeniable sense of loyalty for the Post Office, dubbed by one respondent as a “British institution” and trusted by 92%.

But they said further degradation of the service would lead to the network sliding to an “irrevocable tipping point beyond gradual decline”.

The 14-month study, published by the University of Chichester and West Sussex County Council, is said to be the most comprehensive conducted in the UK on the impact of Post Office closures.

The 100-page report said that by stripping away the Post Office's key benefit of convenience, management was losing the goodwill of customers who would look elsewhere.

The study, carried out Dr David Cooper and Dr Jo Horwood of the University of Chichester, involved more than 400 residents and 200 businesses in West Sussex.

The report follows a study earlier this month which found Post Office customers are waiting longer in queues than a year ago.

Consumer Focus visited more than 400 branches and found average waiting times of six minutes seven seconds, compared with five minutes 40 seconds a year ago - an increase of 7%.

The West Sussex report looked at the impact of Post Office closures in Bognor, Worthing, Horsham, Washington, Graffham and Haywards Heath, which lost 36 Post Offices last year.