SACRAMENTO — A watchdog group is accusing Sacramento Mayor Darrell Steinberg of working out a quid pro quo deal with local construction unions to secure $150,000 in funding for Measure U, a ballot initiative the mayor backs that would raise the city’s sales tax.

“What we have is a series of events and a chronology that is deeply suggestive of something really inappropriate going on,” Eye On Sacramento President Craig Powell said. “Was it just coincidence that first a $100,000 check, then the agreement came, then a final $50,000 check? Or was there a plan?”

In August, the City Council approved a project labor agreement that requires contractors on city public works projects that cost over $1 million to hire mostly union workers — with a few exceptions.

“And they’re able to barricade off any competition from non-union contractors and non-union workers using, essentially, their political pull to win an advantage they can’t win in the marketplace at the cost of taxpayers,” Powell said outside City Hall on Thursday.

Powell wants the public integrity section of the FBI to investigate. Powell is also the chairman of the “No on Measure U” campaign. Steinberg’s communications director Mary Lynne Vellinga says Powell’s claims are political and adds those unions already supported Measure U before the City Council’s vote.

State Building and Construction Trades Council Legislative and Political Director Cesar Diaz sent FOX40 a statement late Thursday afternoon:

“Measure U invests in the City of Sacramento and creates good construction jobs and high quality city services. Our members and their families live and work in and around the Sacramento region. On behalf of the working families of the Building Trades we are proud to support the vital services Measure U would create. The State Building Trades Council has supported public infrastructure investments throughout the state, from San Diego, Los Angeles to San Francisco, Oakland and Sacramento. Our support has helped build and improve public infrastructure such as freeways, roads, streets, bridges, affordable housing, water systems, schools, public transit and other important state and local projects throughout California. We were also supporters of Sacramento’s Measure B from 2016 when then Mayor Kevin Johnson was in office.”

“It’s not a surprise that they would support Measure U because the spending with Measure U will help boost the economy create jobs and create work for union workers,” Vellinga said.

She added that Mayor Steinberg would be open to an investigation into Powell’s claims.

“It’s not really up to him,” Vellinga said. “It’s up to the FBI and I would be very surprised if they were to take this seriously.”

Both sides strongly disagree on the number of construction workers who are non-union in the region.

Eye On Sacramento claims that number is around 90 percent, but the mayor’s office says there are around 2,000 union apprenticeships versus 300 non-union apprenticeships.