Environment minister John Redwood has fanned the flames of his row with the House Builders Federation by claiming again that its members are ignoring a promising market in the inner cities.One house builder said he thought the letter showed Mr Redwood had 'gone mad'. The HBF said inner city schemes are not coming forward because the market is so poor.The row began in August when Mr Redwood called on urban development corporations to release 'sensibly-priced' land for low-cost housing.Builders welcomed this suggestion but were outraged by his comment at the same time that: 'Many house builders have spurned the opportunity of building in inner cities. They thought they knew better, paying extravagant prices for green field sites ... many home builders have gone bust or are in dire financial straits for trusting to conventional wisdom.'HBF president David Holliday said the minister seemed to be saying that builders had brought their problems on themselves.He wrote to Mr Redwood calling for a meeting to clear the air, but his reply to that letter has sharpened the original row.Mr Redwood said: 'I was addressing myself both to the UDCs, who have acquired, assembled and reclaimed land which might now be suitable for disposal for housing; and to house builders who, despite the evidence of the market, are still being cautious in taking up investment opportunities in the inner cities.'I am firmly of the view that there is a market opportunity here which can be exploited to the benefit of both inner city regeneration and the house builders.'I would also like to see the members of your federation initiating proposals for development, which could range in scale from small infill schemes to urban villages.'