The Government plans to begin publishing its own monthly house price index from the beginning of next summer.

The Office of the Deputy Prime Minister said the National Statistics House Price Index, plans for which were unveiled in August, would be based on at least 30,000 sales each month - about a third of all mortgage completions.

But it denied reports that it was introducing the survey because it was worried that figures on house price rises put out by Halifax and Nationwide were stoking the property boom.

Instead it said the index was simply an expansion of the quarterly one that has been published since 1968, based on a five per cent sample of completions from 49 lenders.

It said that after improvements in technology many lenders had indicated they would be prepared to provide data on 100 per cent of their completions, making the sample big enough for the index to be expanded from a quarterly one to a monthly one.

But ODPM said that the Nationwide and Halifax indexes, which are based on the lenders' own mortgage approvals, would still have an important role to play as they reflected house prices six to eight weeks before completion and provided an early indication of house price trends.

Across the UK there are an average of about 120,000 completed house purchases each month. About 25 per cent of these are for cash, leaving about 90,000 bought using a mortgage.