HOUSE PRICES have declined by an average 5 to 6 per cent since April last year, the Halifax Building Society said yesterday. In London and the South-east prices have fallen by up to 15 per cent, while in Scotland prices have risen by more than 1 per cent.

Gary Marsh, senior economist, said that with council tax valuations based on April 1991 estimates, prices had fallen an average 1-2 per cent by the time estate agents began to assign homes to the new tax 'bands' at the end of last year. Since then prices had fallen by 3 to 4 per cent. 'The decline is likely to be around 5 to 6 per cent on average.'

Halifax figures show prices have fallen by 11 per cent in London, 9 per cent in the South- east and 8 per cent in the South-west and East Anglia since the second quarter of 1991. Other regions have seen smaller falls - 6 per cent in the East and West Midlands, 3 per cent in Yorkshire and Humberside and less than 1 per cent in the North. Prices have increased marginally in Scotland.

Morgan Grenfell, the merchant bank, said yesterday prices would fall by between 10 and 15 per cent across the South of England from April 1991 to April 1993 when the new tax is introduced. The rest of England and Wales would see falls of between 3 and 10 per cent. Scottish prices would rise by 7 per cent.

Although Michael Howard, Secretary of State for the Environment, has been warned that as many as 1.5 million householders may appeal against their valuations, Trevor Kent, of the National Association of Estate Agents, said it was too early to say how many will do so.

'The valuations are not to the nearest pounds 50, they are simply to put properties into one of the eight bands. The bands are quite wide and a lot of the properties will remain in the same band after a 5-10 per cent reduction. Even if the reduction means the property would have changed bands the difference in what residents would have to pay could be small. Remaining in Band C ( pounds 52,000- pounds 68,000) instead of falling into Band B ( pounds 40,000- pounds 52,000) would only mean paying an extra pounds 44: pounds 355 according to government estimates for 'average spending' councils instead of pounds 311'.

Michael Pattison, chief executive of the Royal Institution of Chartered Surveyors, said that if the Government failed to carry out regular revaluations, the number of appeals would be high.

He said: 'Ministers say the banding grid is set in stone, with, in the overwhelming majority of cases, homes permanently locked into the bands to which they are now being assigned. If this remains the case there will be a huge volume of appeals.'

(Map omitted)