The number of stores which have been empty for over two years has risen by a fifth as retailers focus on sites in central locations.

The number of retail outlets that have been unoccupied for two years or more was around one in 28 in the year to the April, according to a study by estate agency Colliers.

Rental prices for prime retail sites recorded their biggest year-on-year increase since 2008, up 1.8%.

By contrast, the percentage of the UK’s top 420 shopping areas where rents declined increased for the first time since 2012 – from 5% to 12%.

Colliers head of UK retail Mark Phillipson said: “A while back, a retailer looking to make a presence across the UK would be looking at a minimum of 100 shops. Now, that is probably 20 to 30.”

According to Colliers, prime locations that continue to have strong rental demand include shopping centres such as Cribs Causeway in Bristol and Meadowhall in Sheffield, as well as “cathedral cities and really strong market towns” such as Chichester, Winchester and Guildford.

However, secondary and tertiary towns grappling with unfilled retail sites will likely have a long-term effect on the sector.

“Vacancy going over two years – that is a proper problem because it means those locations are probably never going to be retail again,” said Phillipson.

“Good quality retailers like to be next to each other. Once you get hole appearing, it tends to have a knock-on effect.”

The impact of this is demonstrated by only 30% of BHS 573-strong store estate securing new tenants outside of London since the department store retailer fell into administration last year.

London is also not immune to the falling demand for stores – prime retail rents in the capital rose 3% during the period compared with an 8% jump the previous year, and are expected to be flat in the year ahead.