Exxon Mobil is just one bad apple among a bunch of companies in the extractive industry suspected of holding back on investors, Global Witness said.

The New York Attorney General's office issued a subpoena to Exxon Mobile following a series of reports claiming the company was misleading investors decades ago about the potential impact its sector had on the global climate. Accusations made against the oil company are similar to those made against the tobacco industry, in that it downplayed the threats of its products despite research acknowledging the risks.

Global Witness, an advocacy group working for more corporate transparency, said Exxon's issues are part of a broader issue on concerns about public disclosure.

"The attorney general is right to investigate Exxon -- but they are not the only bad apple," Zorka Milin, a senior legal advisor at Global Witness, said in an emailed statement. "The investigations should be widened and strong laws brought in to make sure oil companies do their business in the open like everyone else."

Global Witness said Shell is among those facing pressure for transparency issues, with corruption risks undermining its business operations in Nigeria. The advocacy group said Shell and Italian energy company Eni "secretly paid" more than $1 billion to gain access to oil basins off the coast of Nigeria.

Ken Cohen, Exxon's vice president of public and government affairs, said recent reporting was inaccurate, deliberately misleading and charged "activists" with exploiting the issue. The company said its research widely mirrored the global understanding of climate issues at the time.