LONDON (Reuters) - Shop rents in the UK fell for the first time since May 2001 in July while commercial property values extended their correction from last summer's peaks to 20 percent, data showed on Tuesday.

Property services firm CB Richard Ellis did not give a specific number for retail rental values but said UK all-property capital values fell by 9.2 percent in the first seven months of 2008.

All-property annual rental growth -- including office and industrial space as well as retail -- in July was 1.8 percent, the weakest since December 2005, as retail property rents followed central London office rents into negative territory, CBRE said.

CBRE is one of the biggest contributors to industry-wide benchmark data from Investment Property Databank, which is used for property derivatives trading and is next due on Thursday.