The Prime Minister's Economic Advisory Council on Thursday advised the government to raise prices of petrol and diesel, along with adjustment of duties, to tackle the upward spiral in global crude prices.

"After making careful assessment of import parity prices so on and so forth, some adjustment in retail prices of petroleum products is also necessary. And that is an exercise that needs to be made," council Chairman C Rangarajan told reporters after releasing the Review of the Economy for 2007-08.

If the global prices of crude remains high at this level, India cannot completely isolate itself from its impact, he said.

Earlier, Rangarajan said: "We had in Petroleum Prices Committee indicated various suggestions as to what can be done. One was that excise duty be made specific instead of ad-valorem, so that the impression is not gained by anybody that when prices rise, revenue would also rise automatically."

He said adjustment could be in various forms including price rise, duty rationalisation and oil bonds. To some extent, burden of rising global crude prices is taken away by the appreciating rupee.

The government has referred the issue of petroleum price revision to a Group of Ministers.

Global oil prices, which rose to 100 dollars a barrel recently, on Thursday went below 90 dollars as traders seized on rising US crude reserves. US President George W Bush also called on OPEC to increase output to help cut the cost of energy.