Monthly reports on house prices from Britain's two biggest lenders - Nationwide BS and Halifax - have a huge impact on sentiment in the housing market.

But their February figures could cause confusion - for while Halifax, part of Lloyds TSB, claims a monthly fall of 0.9 per cent to an average £162,657, Nationwide BS reckons prices went up by 0.3 per cent, to £161,183.

However, Nationwide BS chief economist Robert Gardner acknowledges: "The overall picture is one of a market treading water. Indeed, the three-month-on-three-month measure of house prices, a better measure of the underlying trend, was basically flat in February, at minus 0.1 per cent."

Ray Boulger at independent mortgage adviser John Charcol thinks the disagreements between Halifax and Nationwide BS are becoming too frequent.

"Most house price indices published measure different things and furthermore figures for any given month in reality cover activity for different periods," he says.

"For example the Land Registry figures have the largest sample and hence are the most comprehensive, but they are also the most historic because they are based on when details of completed sales are reported to the Land Registry.

"Near the other end of the timescale, Nationwide BS and Halifax base their figures on mortgage offers issued by those lenders and so are more timely, but they also include figures for some transactions which never actually complete.

"There are good reasons why different indices show different figures for the same month. But Nationwide BS and Halifax indices should be the exception to this, because they are broadly designed to measure the same thing on nearly the same time frame. So why do they often vary so much, particularly on a monthly basis?

"One issue hampering all house price index compilers is the current historically low level of transactions. Unless a provider has significantly increased market share this reduces their sample sizes, which makes it more challenging to make the necessary mix adjustments to reflect any changes in the type of property purchased from month to month."

While Nationwide BS has roughly held its market share in a much smaller market, Halifax's market share has fallen, so its figures are based on a smaller share of a smaller market.

Ray adds: "February figures from each lender provide a good example of how seasonal adjustments seriously distort the way house price changes are reported.

"Halifax reports a seasonally adjusted fall of 0.9 per cent for February but the real change was plus 0.1 per cent, whereas Nationwide reported a seasonally adjusted increase of 0.3 per cent, but its real figure was unchanged on the month.

The news is also more cheerful from Hometrack, the housing market data specialists, which says that market conditions in southern England during February actually improved.

Based on information gathered from more than 5,000 agents and surveyors, Hometrack says housing demand jumped by 14.7% in February, the first increase for eight months, while agents reported a 25% surge in sales agreed.