BOSTON (AP) – Gov. Deval Patrick said Tuesday he made a mistake by calling a top official at Citigroup on behalf of a struggling lending company on whose board he once served.

Patrick issued the mea culpa in response to a Boston Globe story reporting he made the call on Feb. 20 to Citigroup’s Robert Rubin on behalf of ACC Capital Holdings while ACC sought an infusion of cash from Citigroup.

ACC is the parent company of Ameriquest, a mortgage company that has been accused of predatory lending practices. Patrick resigned from a $360,000-a-year position on ACC’s board of directors last May, saying he needed to focus his attention on his gubernatorial campaign.

Rubin and Patrick worked together in the Clinton presidential administration when Rubin was treasury secretary and Patrick was an assistant attorney general.

A watchdog group had questioned why Patrick would call a corporation whose interests in Massachusetts are regulated by the state.

“As a former board member, I was asked by an officer of ACC Capital to serve as a reference for the company and agreed to do so,” Patrick said in a statement issued Tuesday afternoon. “I called Robert Rubin, a former colleague from the Clinton administration and an executive at Citigroup, to offer any insight they might want on the character of the current management. The conversation with Mr. Rubin lasted at most a couple of minutes.

“Even though I made this call solely as a former board member, and I believe that was clear to Mr. Rubin, I appreciate that I should not have made the call. I regret the mistake.”

Patrick’s connection to Ameriquest drew criticism during the campaign because the company has been accused of predatory lending. Ameriquest provides high-interest mortgages to buyers with risky credit histories.

Pam Wilmot, executive director of the government watchdog group Common Cause Massachusetts, said such a call creates an appearance of conflict of interest.

“When a governor calls a company, particularly one that does business with the state, and asks it to do something, the company is going to feel pressure to act,” Wilmot told the Globe.

Citigroup is the world’s largest financial company.

It was the second time in less than two weeks that Patrick acknowledged a judgment error after media accounts about him. On Feb. 22, he said, “We really screwed up,” after announcing he personally would repay the $27,000 to the state for new furnishings in his Statehouse office and would pay the $500 monthly difference in the cost of leasing a new Cadillac to replace the Ford Crown Victoria used by former Gov. Mitt Romney.