NEW YORK (Reuters) - Several big fund firms supported challenges on executive pay or climate disclosures less frequently where they had business ties to energy companies and utilities, according to a new study released on Tuesday.

The scrutiny of firms including Vanguard Group and Invesco Ltd is the latest research to raise questions about how well they manage potential conflicts of interest when casting proxy votes at the same time they are trying to win work like running corporate retirement plans.

“The business relationships seem to have an impact on how the managers are voting,” said Edward Kamonjoh, executive director of the 50/50 Climate Project. The Washington, D.C.-based nonprofit, which issued the report, looks to help investors and corporations work on issues like climate change.

Fund firms often are the largest shareholders of publicly traded U.S. firms, giving their votes outsized influence. Meanwhile climate and other governance matters promise to be hot topics in the shareholder meeting season this spring after Vanguard, BlackRock Inc and others have revised their policies on the area.

For its study 50/50 reviewed how fund firms voted on 27 proxy questions last year at oil and gas companies and utilities, tracking how often they voted against management recommendations.

At Vanguard, for instance, 50/50 found the $4 trillion Pennsylvania index fund manager broke from management 22 percent of the time. But at four companies where Vanguard serviced retirement plans, its funds did not support any challenges.

The votes could have mattered such as at Chevron Corp where 46 percent of votes cast opposed top executives’ pay and Vanguard owned 6 percent of shares. Vanguard funds also opposed a resolution calling for Chevron to disclose the business impact of a rise in global temperatures, which won 41 percent support.

Vanguard spokeswoman Arianna Stefanoni Sherlock called the concerns raised by the study “unfounded” and said its voting operations are independent of its servicing work.

Vanguard changed its voting policies this year to leave itself more room to support environmental measures that create long-term shareholder value. Sherlock said the update was meant to showed the types of proposals it might support, and to eliminate abstentions.

Another fund firm, Invesco, broke with management 12 percent of the time, and at none of seven companies where it had business ties.

Invesco spokeswoman Jeaneen Terrio said where a conflict of interest may exist it will vote by policy or by a committee that excludes marketing and other customer-facing personnel.