Government urged to fund speedy resolution of business rate disputes
A fifth of business rate appeals across England and Wales remain unresolved under the previous measure for calculating the tax.
The Valuations Office Agency (VOA) said it had received 1.1 millions challenges to the 2010 property valuation, of which 233,550 were still outstanding.
The move could spark tax rebates for the past seven years.
However, the latest figures do not include any challenges to the business rates since April 1 when the rateable values were updated.
The Government has set aside £1.3 billion for tax rebates against the new property valuations.
Business rent and rates specialists CVS said the government agency would have to tackle the backlog despite looking to slash its workforce by a third over the next three years, losing 1,000 staff.
CVS chief executive Mark Rigby said: "It is foolhardy of the Government to think that strategic statutory functions of providing fair and accurate property valuations can be maintained with business rates appeals being resolved quickly and efficiently whilst slashing resources and haemorrhaging experience and expertise.
"The overwhelming consensus is, and remains, that The Valuation Office Agency needs greater funding otherwise it's been totally disingenuous to increase the yield by £1.3 billion this year to provide for losses on appeal through tax rebates."
A spokesman for the VOA said: "We have cleared on average 45,000 appeals per quarter over the last nine months, and we continue to clear outstanding appeals.
"These figures show that we are actually clearing more appeals than we did for the same period in the previous rating list so questions of under-resourcing are unfounded.
"The Government introduced check, challenge, appeal (CCA) to reform the appeals system.
"The previous appeals system was broken.
"These statistics show that more than 70% of challenges against the rating list resulted in no change, showing why the Government had to reform the business rates appeal system.
"Processing this volume of claims caused delay and uncertainty for the business and local government and cost into the system."