The Westcountry's leading estate agent has dismissed the latest reported surge in house prices by a high-street mortgage lender as "total rubbish".

Richard Copus, spokesman for the National Association of Estate Agents in the South West, said claims that detached houses had increased in value by 13 per cent during the past year were "irresponsible".

A survey this week by the Halifax said detached homes had outperformed all other property types and now sold for an average £299,295.

The group said price gains for semi-detached, terraced homes and flats were between 8 and 9 per cent during the year ending in June, considerably higher than figures from the Land Registry.

Mr Copus said: "I don't know where they get these figures from but they certainly don't relate to Devon and Cornwall.

"Detached houses are always going to be worth more but actually, at the top end of the market, prices have dropped because the City bonuses are no longer there.

"These statistics are just so erroneous and no responsible seller is going to make such claims – it is total rubbish."

A rash of absurdly differing recent reports has prompted a Government review of its own house price indices, the Land Registry and CLG (Communities and Local Government) surveys.

The Office of National Statistics will also look at other house price surveys and report by the end of the year.

Mr Copus says prices have risen by around 3 to 4 per cent in the region.

He suspects companies are cherry picking figures, particularly in urban areas where detached properties are scarcer, and proportionally more expensive than the rest of the market.

"Quite often they take a sales figure before the surveyor has pulled the property to bits and forced a renegotiation and lowering of the price," he added. "The only accurate criteria is the Land registry but their figures but they are four to five months out of date."

The Halifax claims the average cost of a detached home was 63 per cent more than the average UK house price during the second quarter, a rise of around £91 a day. It compares this to semi-detached properties which saw the biggest gains during the past decade, with the value soaring by 111 per cent since 2000.

The average cost of a terraced property has jumped by 110 per cent during the same period, while bungalows rose by 109 per cent and detached homes by 102 per cent.

Suren Thiru, Halifax housing economist, said: "Detached properties are likely to have benefited from greater demand from those buyer groups currently most able to enter the housing market."

The research comes the day after economists warned the housing market was set for more price falls after lending levels remained subdued.