Organizers of the campaign to repeal California's latest gas-tax increase are accusing the state's transportation department of illegally directing one of its contractors to stop traffic on a major highway to pass out leaflets opposing the repeal.

A video taken Tuesday of the incident along State highway 78 in San Diego County shows a Caltrans contracted worker responding to a driver's questions about why he and other workers are stopping traffic with hand-held stop signs and approaching cars to hand-out a "No on Prop 6" flyer.

"Hi, what do you got there?" the driver asks.

"Flyers to let you know about that proposition," a worker in a hard-hat, orange shirt, and reflective vest responds.

Pressed further, the worker then goes on to say that he and others passing out the flyers are "working with Caltrans" and "they just told me to hand it out."

The workers handing out the flyers appear to be employed by Manhole Adjusting Inc., which was awarded a Caltrans contract to perform work along the stretch of roadway during the summer and fall months.

Carl DeMaio, who is leading the repeal campaign, said Caltrans, the state's transportation department, was involved in the effort from the video footage and photos taken of road workers passing out the leaflets.

"This proves once again that Caltrans simply cannot be trusted to what is right with our gas-tax funds—they literally are using gas tax funds to support the distribution of campaign materials to raise the gas tax on working families," DeMaio said.

California voters, who pay some of the highest gas prices in the nation, will decide in November whether to overturn the most recent 12-cent increase in the state's gas tax, along with other new fuel and vehicle fees. The campaign to repeal the gas tax will appear on the ballot as Proposition 6.

Republicans hope the issue will also boost GOP voter turnout across the state in the critical fall congressional mid-term elections.

Opponents have public opinion on their side as more than 51 percent of registered voters across the state favored repeal, with the numbers ticking higher in more conservative congressional battlegrounds.

Proponents argue that the new 12-cent-a-gallon gas tax is needed to fund nearly $5 billion in road construction and mass transit costs.

Calling for an immediate investigation and the eventual prosecution of the individuals involved, DeMaio has sent complaint letters about the traffic-stopping incident to the San Diego County District Attorney's office and the California Highway Patrol, and has filed an ethics complaint with the California Fair Political Practices Commission.

He compared the incident to the infamous "Bridgegate" scandal in New Jersey that doomed then-New Jersey governor Chris Christie's GOP primary campaign. Christie allies eventually went to prison for engineering lane closures at the George Washington Bridge in alleged retaliation against a Democratic mayor who didn't endorse the governor.

The cases are similar in that they involve allegations that taxpayer-funded resources were being used to purposefully stop or snarl traffic, which is illegal in both states.

"There is no grey area here, Caltrans is caught in blatant violation of California law that prohibits the use of taxpayer funds for campaign activities or advocacy," DeMaio said Wednesday.

DeMaio also released several photos of the workers and trucks emblazoned with Manhole Adjusting Inc. and Caltrans logos stopping traffic, as well as a statement from a witness whose car was stopped that day by what he said appeared to be a Caltrans worker. The worker, he said, knocked on the window of his car and handed him the "No on Prop 6" flyer.

"I and other drivers stopped were not free to leave and were at the sole mercy and direction of this government-funded campaign worker," the witness said. "If I had known this was a campaign, I would not have rolled down the window for this person."

A leader in the "No on Prop 6" campaign issued a statement saying the group had no knowledge of the leaflet distribution.

"The No on 6 campaign very carefully follows all rules prohibiting the use of public resources for campaigning and often reinforces those rules to anyone involved with the campaign," said Michael Quigley, executive director of the group California Alliance for Jobs, which opposes the gas-tax repeal. "We had no knowledge of this incident but denounce any inappropriate use of public resources or venues for campaign purposes."

Caltrans Director Laurie Berman released a statement saying the agency is looking into the matter and noted that the individuals passing out the leaflets were private contractors, not Caltrans employees.

"Regardless, the Department does not condone political advocacy or the distribution of campaign information on work project sites and is contacting its contractors to remind them of this."

Caltrans declined to answer further questions.

DeMaio dismissed the claims of ignorance about the leaflet distribution by road workers.

"How can [No on Prop 6] possibly disavow knowledge of this when a box of their materials was found on site," he said, noting that the flyers contain notices that they are paid for by the "No on Prop 6" campaign. "Clearly they coordinated this. This is a criminal violation that they will have to account for."

He also pointed to a business card of a Caltrans engineer provided by the road workers passing out the leaflets when asked who to contact about the propriety of the leaflet distribution.

California law specifically states, "it is unlawful for any elected state or local officer, including any state or local appointee, employee or consultant, to use or permit others to use public resources for a campaign activity or personal or other purposes, which are not authorized by law."

Another traffic-related law bars anyone from bringing a vehicle to a complete stop on the highway "so as to impede or block the normal and reasonable movement of traffic unless the stop is necessary for safe operation or in compliance with the law."