City Councilman Robert Jackson pictured with Speaker Christine Quinn and UFT President Michael Mulgrew in 2011 on the first day of school.

The super PAC for the city teachers union may have violated campaign finance rules by not disclosing spending details for a robocall sent to voters during the 2013 primary elections, GothamSchools has found.

A Sept. 8 phone message touting Robert Jackson’s education credentials was paid for by the union’s independent expenditure group, called United for the Future, according to a recording of the call obtained by GothamSchools from a Manhattan voter who received the message. Jackson, who at the time was enmeshed in a tight primary for Manhattan Borough President, had received the United Federation of Teachers’ endorsement.

But the union failed to disclose the call to the city’s Campaign Finance Board, a requirement designed to improve transparency around spending by outside interest groups. The union reported spending only $12,234 on Jackson for a mailer sent on Sept. 6, filings show.

“I think it raises serious questions,” said Alex Camarda, director of public policy at Citizens Union, a good government organization.

“What about all the other candidates that the UFT endorsed?” Camarda added. “This might not be limited to just Robert Jackson.”

A Campaign Finance Board spokesman said the board would include the robocalls in its review of whether outside interest groups such as the UFT conformed to finance rules in the primary election. The rules are in place to limit the influence that groups are able to exert over elected officials.

Earlier today, the board fined one such group for failing to use a “paid for by” disclaimer on phone recordings that the group had funded.

The UFT’s spending landed under scrutiny this week when Crain’s New York Business reported about the union’s relationship with an embattled political consulting firm. The firm, the Advance Group, kept both the UFT and candidates who were endorsed by the union on its client list at the same time.

The union paid the Advance Group at least $370,000 for work on the 2013 elections, but reported that spending under the guise of a fake firm called “Strategic Consultants, Inc.,” Crain’s revealed. The firm was listed for the Sept. 6 mailer for Jackson, as well as other candidates who received the union’s endorsement.

These candidates had also hired the Advance Group to work directly for their campaigns. Of $1.2 million that Jackson’s campaign reported spending during the election, Advance Group collected more than $871,000 of those payments.

Groups can spend unlimited amounts as long as they do not coordinate their spending with individual candidates and their campaigns. But Camarda said the union’s phony reporting made it “hard to imagine that there’s not coordination going on.” Unless, Camarda added, “the Advance Group has created some kind of firewall to prevent that.”

A spokeswoman for the Advance Group did not return emails and phone calls requesting comment. Jackson did not respond to a call and an email seeking comment.

UFT President Michael Mulgrew said that the union was in full compliance with campaign finance rules.

“We happily comply with all campaign finance board rules and regulations and we have written assurances from anyone who we were working with that they were complying with the same rules and regulations,” Mulgrew told reporters yesterday.

Mulgrew added that he was prohibited from communicating about political activities with United for the Future. Paul Egan, the UFT’s political director who is listed as the PAC’s representative did not respond to emails about the robocalls.

United for the Future spent over $3.3 million on 37 elections, including $2.7 million on Bill Thompson’s mayoral campaign.

UFT’s undisclosed robocall for Robert Jackson: