A COSTLY council tax bombshell "timed to explode" after the General Election is awaiting residents in York and North Yorkshire, an MP warned today.

Tory Anne McIntosh said a revaluation of properties may send thousands of bills for average homes soaring by more than £250 each.

Conservatives are warning one in three homes could be bumped into a higher valuation band - amid fears the York and Selby area will be one of hardest hit by changes because of its sky-high property prices.

Miss McIntosh raised concerns about the "rigged" revaluation process, but the Government dismissed such claims as "speculation".

She said: "I fear the coming revaluation will be fiddled to increase local tax bills by stealth. Even without any change in the headline rate of council tax, homes will face larger bills.

"A rigged revaluation could push the average home in the Vale of York up a tax band - meaning an automatic hike in council tax bills hitting the doorsteps.

"This threatens to be a ticking council tax bombshell: intentionally primed to explode after the General Election."

She said Conservatives would stop plans for a "rigged" revaluation, and bring in extra measures to keep council tax down.

City of York Council finance chief Simon Wiles admitted the authority was concerned about the revaluation.

Rough estimates indicate a third of York's 80,000 homes - mostly currently made up of Bands B, C and D - could be bumped up a band.

He said: "We are very worried, particularly in the light of high house price increases in York in recent years. There's a concern that residents could end up paying more, yet this would provide no extra resources for the council."

The revaluation process is due to start next month, with each home re-assessed and new bills issued in 2007. The current banding system is based on 1991 house prices.

In Wales - two years ahead of England in the revaluation process - four times as many homes are moving up a council tax band as are moving down, Tories claim.

Based on the new Welsh tax bands, the Conservatives say the average home in North Yorkshire, could be forced up a tax band, for example, from Band D to E, typically adding £267 to a bill.

But a spokesman for the Office of the Deputy Prime Minister said: "Revaluation is not about raising more money, it's about fairer distribution. Policy has not been decided yet, so you can't say that Band D is likely to go up £250."

Responding to fears that York residents may be hit harder because of the property boom, he said the city was not alone in experiencing higher house prices in England, and revaluation would take this into account.

Updated: 08:30 Wednesday, March 16, 2005