A Boston-based sneaker manufacturer under fire from gay rights activists is seeking to distance itself from a political donation by its chairman, who gave $500,000 to an independent group supporting Republican Mitt Romney for president.

Jim Davis, chairman of New Balance, gave the money on June 15 to Restore Our Future, a “super PAC” focused on supporting the former Massachusetts governor’s bid for the White House.

Gay rights groups have criticized the donation in the wake of Romney’s decision last week to sign a pledge supporting a constitutional amendment barring same-sex marriages.

New Balance President Rob DeMartini said in a statement posted on the company’s Facebook page that the contribution was “a private donation” unconnected to the company. The company, based in a state that allows same-sex marriages, has often emphasized its diversity policies.

“Mr. Romney’s position on this issue is not reflective of Jim Davis’, my or New Balance’s position and support of the gay, lesbian, bisexual, transgendered community,” DeMartini wrote. “As a company, New Balance embraces the differences in all people and we work tirelessly to create and sustain an environment where everyone — our associates, consumers, customers and guests — are treated with dignity and respect.”

The New Balance case illustrates the perils to corporations and candidates alike of a freewheeling money system that has sprung up outside the traditional campaign structure. Retailers Target and Best Buy faced boycotts last year after their contributions to a Minnesota business group helped support a Republican gubernatorial candidate opposed to same-sex marriage.

The statement is also the latest controversy to erupt over donations to Restore Our Future, which was formed by three former Romney aides and does not have to abide by spending or contribution restrictions.

A $1 million contribution to the group came under fire from good-government activists last week because it was made through a dummy corporation that seemed designed to hide the identity of the donor. Longtime Romney supporter Edward Conard eventually revealed himself as the person behind the arrangement.

Both incidents underscore the fast-evolving landscape surrounding campaign spending, which has been made easier and, in some cases, more secretive by a Supreme Court ruling allowing corporations, unions and nonprofits to spend unlimited funds on elections. Dozens of super PACs have sprung up in the wake of the decision on both sides of the political aisle.

Restore Our Future, which must disclose its donors to the Federal Election Commission, raised more than $12 million in the first six months of this year for its pro-Romney effort. Romney is barred from coordinating directly with the group, but he has helped to raise money for it by appearing at fundraising events, officials have said.

Spokespersons for the Romney campaign and the super PAC had no comment.