Secondary office property may fare worse than retail in 2013 if todays announcement by Segro of it's revaluation loss in it's UK office portfolio is anything to go by. Shares in Segro, the U.K.’s largest owner of industrial properties, fell the most in more than five months after the value of its portfolio decreased in the second half of last year.

The shares dropped as much as 3.9% in London trading, the most since Aug. 1. Segro’s property portfolio fell by around £180 million, led by a £75 million reduction for offices in the Winersh Triangle and the Bath Road, Slough.

In a conference call Segro said that CBRE had revalued the portfolio and had been especially hard on the Thames Valley offices. The value of these in Q2 had fallen by 13.1%. This is because banks will not fund short lease investment property, so without debt funding there is little cash around for such assets.

The revaluation “reduces the expected Dec. 2012 net asset value to 295 pence,” Kate Barlow, a Peel Hunt Research analyst, said in a research note. That’s 4% less than the 307 pence analyst consensus, she said.

The value of Segro’s offices in Pegasus Park, Belgium, and Vimercate, Italy, fell by 28% to £50 million giving an 11% yield, while the remaining £25 million  decline came from undisclosed assets, the statement said. The company’s shares were down 2.1%, or 5.27 pence, at 246.03 pence as of 14.13 p.m., giving the company a market value £1.82 billion.