Commercial property group Hammerson nearly doubled losses in the last half-year though it added there are signs property markets may be stabilising in both France and the UK.The group, which raised £584m through a deep discount rights issue in March, posted an increased loss of £819m in the half-year to June, up from £417m, as its portfolio value dropped by 27% to £4.75bn. NAV fell by 27.7% to 373p. "Prime UK yields now stabilising," Hammerson said. "While there was a 14% underlying decline in the portfolio capital value during the first half of 2009 (UK: -15%, France: -11%), yields on UK prime property are now stabilising," it added.Rental income rose to £156.4m from £145.8m, but the level of void rose. The overall occupancy level at 30 June was 92.6%. Excluding recently completed developments the figure was 95.7%, compared with 97.2% at 31 December 2008, Hammerson said.The group also announced that chief executive John Richards is to retire to be replaced by David Atkins. Richards, 53, says he wants a bit of a rest after a tough year."I've done 10 years and the last year has been pretty hard work with the rights issue and the sales and some tough economic conditions. I'm going to take a bit of a rest." he told reporters.The interim dividend is 6.95p against 12.6p.