New Delhi, Sep 25 - A senior Left party leader has asked Prime Minister Manmohan Singh to 'immediately' launch a probe against Director General Hydrocarbons V.K. Sibal, who allegedly took favours from the Mukesh Ambani-led Reliance Industries Ltd (RIL).

'The CBI (Central Bureau of Investigation) should be directed to immediately launch an enquiry into all approvals of capital expenditure accorded by Sibal during his five year tenure to all operations including Reliance (Industries),' Suravaram Sudhakar Reddy, deputy general secretary of the Communist Party of India (CPI), said in a letter to the prime minister.

Reddy, who is a former Lok Sabha member, also said: 'The government should ensure that the petroleum and natural gas ministry's request to give a two-year extension to Sibal is immediately withdrawn.'

Referring to reports and articles appeared on the media, Reddy said the ministry and Sibal had played a vital role in the hasty approval of the hike in the capital expenditure of Reliance Industries for the Krishna-Godavari basin from $2.4 billion to $8.8 billion.