NEW DELHI: The government on Wednesday re-estimated the GDP linked to 2011-12 prices, which lowered the growth rates during the UPA regime, prompting the Congress party to slam it as the desperate attempt of a "defeatist Modi government " to undermine the growth story over the last 15 years.The back series data from 2004-05 to 2011-12 showed that GDP growth rate in 2011-12 has been revised down to 5.2 per cent from the previous 6.6 per cent expansion which was based on the 2004-05 base year.Similarly, growth for 2010-11 has been pared to 8.5 per cent from the earlier 10.3 per cent under the old series. The base year is revised periodically to reflect the changes taking place in the economy.The Central Statistics Office (CSO) back series data is in sharp contrast to the numbers released by a panel on real sector statistics set up by the National Statistical Commission.The report by the panel headed by Sudipto Mundle, emeritus professor at the National Institute of Public Finance and Policy, had shown that the economy had grown by 10.8 per cent in 2010-11. But the government had said the data provided by the panel was "not official," triggering a war of words with the opposition party.The Congress was quick to criticise the latest CSO numbers. "Modi government and its puppet Niti Aayog want the people to believe that 2+2=8! Such is the gimmickry, jugglery, trickery and chickanery being sold as "back series data," the party said in a statement.In the run-up to the 2019 general elections a sharp political debate has erupted over the Modi government's handling of the economy and the latest data is expected to trigger sharp responses from both sides. Following the new data, the average growth during the 10 years of UPA works out to 6.8 per cent while the NDA's four-rule has seen average growth of 7.3 per cent.A senior government official said it was only fair that the growth rate in the previous years is re-estimated using the 2011-12 prices when the current growth rates are being based on this data.The back series data was released after it had been checked for its methodological soundness by leading statistical experts in the country. Government think tank NITI Aayog had organised two round tables in which domain experts participated to ensure the quality of coverage and methodology."The new data released today by CSO for 2004-05–2011-12 based on 2011-12 base year is significant improvement both for coverage and methodology. The new series, with its supporting back series, is internationally comparable and is in sync with UN Standard National Account," Niti Aayog vice chairman Rajiv Kumar said.Kumar said it was distressing to read the Congress statement. " They are completely denigrating the intellectual and technical competence of not only the CSO experts but also the 10 leading statisticians who had rigourously examined, vetted and vouched for the rigour of the back series data," Kumar told TOI.Chief statistician Pravin Srivastava said the new methodology adopted for the data was robust and globally comparable.The statistics office had released the new series of national accounts, revising the base year from 2004-05 to 2011-12 in January 2015. It said that the methodology for preparing the back series estimates is "largely the same as the methodology followed in the new base year."Former chief statistician T C A Anant said the Mundle committee was an academic exercise, was not official and had limited applicability. He said it had made several important recommendations and to view it only through one element would be wrong.He said the CSO had done a fair job with the back series numbers given the data availability. "It is a fair exercise and it is complete," Anant said referring to the CSO data.Another former chief statistician, Pronab Sen said by getting the Niti Aayog to release the data the entire process has been politicised. "This is the first time somebody other than the CSO has released the GDP data. Earlier the PM and FM came to know about the data when it was released by CSO. This was completely unnecessary," Sen said. "I have no doubt the CSO has done a good job but this was unnecessary," he added.An independent economist said divergence in estimates is not surprising. "Two economists will have three views," he said, declining to be named.