TI report, which placed 42 oil and gas companies into three tiers based on their level of transparency in revenue disclosure, clubbed ONGC with China's CNOOC and CNPC, Russia's Lukoil and US-based ExxonMobil Corp in the lowest tier for disclosing information only by geographical segment and providing almost no additional information.
According to the report released on Monday, Royal/Dutch Shell, Brazil's Petrobras, Norway's StatoilHydro, BG Group of UK and Petro-Canada were among the best performing companies.
TI used publicly available records to measure companies' payments to host governments, their operations and contributions to corporate anti-corruption programmes.
ONGC, it said, faired in the top tier when it came to disclosure of revenue at home, providing information about regulatory structure and procurement practices and disclosure of anti-corruption
programmes.
However, when it came to operations outside home country, ONGC fell in the lowest tier for disclosing only by geographical segment and providing almost no additional information relevant to revenue transparency, the report said.
"Further improvement for this group required increased reporting on all areas of revenue transparency," it added.
BP Plc, Chevron Corp, Conoco-Philips, Eni of Italy and Total of France were in the middle tier of companies that disclose revenue by geographic region and could improve by giving a country-by-country breakdown.
Firms in the highest tier disclose payments systematically on a country-by-country basis and go beyond the mandatory reporting regulations.
