The fertiliser industry on Monday criticised the revised pricing norms finalised by government for urea units retrospectively from 1997 thanks to which, fertiliser companies will have to pay back over Rs 1,800 crore to the government. This too for the last four years for which fertiliser companies have already closed their accounts.‘‘Adverse changes have been made in the basic parameters of pricing with retrospective effect and well after the industry has finalised its accounts, declared profits and paid dividend and taxes thereon,’’ Fertiliser Association of India (FAI) said.In a release issued here on Monday, the fertiliser industry, resenting ‘‘negative changes’’ in the retention price scheme (RPS) with retrospective effect in 7th and 8th pricing periods, FAI said it would be ‘‘very difficult for the industry to pay back over Rs 1,800 crore in addition to Rs 1,374 crore already recovered from it.’’ In fact, such retrospective changes in policy, going back as far as five years, ‘‘is like changing the rules of the game after the match is over, and changing the result earlier declared,’’ FAI stated. Among the adverse changes, capacity utilisation norm is being changed that would further lower rate of return envisaged under the scheme.