Oil and Natural Gas Corporation on Tuesday made last minute changes in the draft 'red herring' prospectus for the public issue of 10 per cent shares of the government and the preliminary offer document is now likely to be filed with the Securities and Exchange Board of India on Wednesday.

ONGC board members fine tuned certain risks and management view of the company's business to incorporate views of the petroleum ministry, which delayed the filing of the prospectus.

"The prospectus in all probability will now be filed tomorrow," a senior company official said in New Delhi.

ONGC has proposed to offer 14.2 crore (142 million) equity shares in lots of 10 with a view to attract retail investors. Of the 142,593,399 equity shares being offered through the book building route, 10 per cent have been reserved for the employees of the company and employees of its subsidiary firms like MRPL and OVL.

Of the remaining shares, as much as 50 per cent stake would be allotted to qualified insitutional buyers, while 25 per cent each would be reserved for retail investors and high networth individuals, the official said.

ONGC public issue will hit the market on March 2 and remain open for bidding in a price band that will be decided a day before the issue opens, till March 10. The company has proposed a wider price band to take care of the price volatility.

After the draft red herring prospectus is approved by Sebi, the offer document will be filed with the registrar of companies by February 10 and roadshows to attract foreign and domestic investors are planned from February 22.