Official figures have overstated the number of cattle herds with tuberculosis in the past two years, it has been admitted.
Figures showing the incidence of new cases of the disease and the number of herds under restrictions following an outbreak of TB have been suspended dating back to September 2011, after a problem was identified with data recording.
The revelation is the latest issue to beset the Government's controversial policy to tackle TB in cattle, after efforts to cull badgers - which can spread the disease to herds - failed to kill enough badgers in two pilot areas, and policing costs spiralled.
A number of herds which had been declared TB-free and had seen their restrictions lifted were still being recorded as not officially free of the disease, officials said.
Figures for the number of herds under restrictions in 2012 and 2013 were likely to be revised "significantly" downwards following the identification of the problem by the Animal Health and Veterinary Laboratories Agency (AHVLA), the Environment Department (Defra) said.
There was also a possibility the problem with the data could affect the figures for the incidence of new cases in herds, although this was unlikely to have a significant effect.
But the figures for the incidence rate had also been suspended pending investigation as a precautionary measure.
The latest figures for the number of cattle compulsorily slaughtered after they were found to have TB or be directly in contact with the disease was still published and showed 27,474 animals were killed from January to October 2013, compared to 31,143 during the same period in 2012.
Dominic Dyer, policy advisor for wildlife charity Care for the Wild, said the announcement that the number of herds with TB had been overstated seriously undermined a key element of the Government's justification for its "disastrous" badger cull policy.
"It has now become clear that Defra has been significantly overstating the number of herds with TB since September 2011. This in turn has misled farmers, MPs, the media and the general public on the extent of the bovine TB problem in the UK.
"We have just spent at least £7 million on the most expensive and disastrous wildlife cull on record, while the level of TB in cattle herds has been dropping by more than Defra estimated.
"It's now time for Owen Paterson to come clean and accept that TB rates are falling significantly in UK cattle herds and that there is no scientific, economic or animal welfare justification to continue the disastrous badger cull policy."
He said the figures also showed the number of cattle slaughtered because of TB had dropped by more than 11% on last year's numbers.
A spokesman for Defra said the AHVLA was amending the statistics after the problem came to light, and those statistic that had been affected had been suspended and would be republished soon.
"This relates to data-entry only and does not affect farmers or have any impact on disease control. This does not change the need to use every tool we have to reduce the unacceptably high levels of TB," he said.
An AHVLA spokesman said: "AHVLA is undertaking urgent work to update the missing statistics with the correct data. This issue relates to the reporting of statistics and does not affect farmers or have any impact on disease control."