(Adds details, context about proposals, and quote from Teamsters official)

BOSTON/NEW YORK May 25 (Reuters) - A majority of Amazon.com Inc shareholders on Wednesday voted against each of 15 investor-led resolutions that challenged the company's policies - including its treatment of workers and use of nondisclosure agreements, an executive said at its annual meeting.

The total number of investor resolutions, including one introduced at the online meeting, was a record for the retail and cloud computing giant, as socially minded investors scrutinize its treatment of workers.

Amazon General Counsel David Zapolsky said that a majority of shares at the meeting were voted against on each shareholder resolution, but he did not give more specific details on the vote results, due in coming days. The overall balloting represented a setback for proponents including unions and civil rights groups that had hoped to gain more support for reform ideas.

While the resolutions were non-binding, companies often take some form of action if they receive backing of 30% to 40% of votes cast.

Investors backed proposals to approve executive compensation, to elect the company's director nominees, and for a stock split.

Marvin Owens, chief engagement officer at Impact Shares, an issuer of exchange-traded funds that voted for the majority of the resolutions, said the results suggest Amazon's largest investors pay more attention to climate and environmental business matters that are easier to quantify compared with social problems.

"The largest investors are reverting back to what they see as areas where there is the most clarity," Owens said.

Said Antoine Argouges, chief executive officer of activist investor Tulipshare, which had sponsored an unsuccessful call for an audit of warehouse workers' wages and conditions, said "I still am trying to get my head around where we failed to convince other investors that it is the right strategy for the company to treat these workers better."

Amazon, the second-largest U.S. private employer, has pressed hard against labor efforts to unionize its workforce. The upstart Amazon Labor Union scored a win in April when workers at a Staten Island, N.Y warehouse voted to join the organization, but then lost a second contest this month.

At Wednesday's meeting, Amazon Chief Executive Officer Andy Jassy defended the company’s record on safety and reviewed steps it has taken to reduce injury rates ranging from new anti-slip shoes to software meant to predict and prevent repetitive stress injuries.

He conceded that injury rates could be affected by the rapid hiring of new workers during the pandemic, including about 300,000 workers in 2021 alone.

"When you hire a lot of people, your (injury) rates tend to go up," he said.

Amazon had recommended voting against all the shareholder resolutions, which came as tech company shareholders push for more transparency on questions such as pay equity, workplace culture and safety, and other environmental, social and governance (ESG) issues. New securities rules have also made the resolutions easier to bring to a vote.

About 13% of Amazon's voting stock is controlled by company founder and executive chairman Jeff Bezos, raising the bar for any effort to win a majority of investor support. (Reporting by Ross Kerber in Boston, Arriana McLymore in New York and Eva Mathews in Bengaluru Additional reporting by Simon Jessop in London Editing by Peter Henderson, Matthew Lewis and Bernard Orr)