There is uncertainty over the precise carrying value of investment properties and sites owned by Castlethorn Construction, one of the country's largest developers led by Joe O'Reilly, the firm's auditors have reported.

Economic developments, in particular the downturn in the property market, have created an uncertainty about the "appropriateness of the carrying value of the investment property and stock of sites", the auditors, BDO Simpson Xavier, have reported in company filings.

The financial statements for the company are not qualified and no adjustments have been made that would reduce the value of investment property or sites involved.

Castlethorn, which is an unlimited company, holds sites for development and "related work in progress''.

Castlethorn was set up by Joe O'Reilly, the late Liam Maye and John Fitzsimons. O'Reilly and Maye's family each have a 40% stake in the company.

They are best known for the Dundrum Town Centre in south Dublin which opened in 2005 and recently received planning permission to develop another phase of the scheme on the site of the old Dundrum shopping centre.

Castlethorn started out developing houses, making significant profits from schemes in Castleknock and Lucan. It has also developed housing in Beaumont and Blackrock in Dublin and owns the Griffeen Centre in Lucan.

It is developing several thousand homes in Adams­town near Lucan and has plans to develop a €500m retail centre there. It also bought Woodbrook, a 52-acre site at Shankill, Co Dublin, for a reported €160m and is also planning to develop housing, offices and retail units there.