Supporters and opponents of a proposal that would allow the city of San Diego to outsource jobs squared off at City Hall Monday.

Following a bus tour dubbed “The Competition Express,” San Diego City Councilman Carl DeMaio and his supporters arrived Monday morning to deliver 138,000 signatures to the city clerk. The signatures are in support of the outsourcing measure’s placement on the November ballot.

Opponents of the measure and groups who said DeMaio’s measure would destroy the city’s living wage also gathered to express their displeasure, and several confrontations between the groups escalated from yelling to physical contact. However, police quickly calmed down the crowds.

DeMaio said he had no choice but to place the measure on the ballot in order to enforce the terms of Proposition C, which voters passed in 2006. Prop. C mandated managed competition, where city departments would compete with private companies for job contracts.

Opponents of the measure said DeMaio’s proposal would do more than that, however. They also said, at the very least, DeMaio was mischaracterizing his ballot initiative.

“It says the city cannon require any contractor to pay anything more than the state minimum wage. That would take working families who are making $27,000 a year for full-time work down to $16,000,” said Susan Duerksen of the Center on Policy Initiatives.

But DeMaio said opponents of the measure are just fronting for organized labor. He said it is time to break labor’s chokehold on City Hall.

“It’s actually the labor unions who say that they don’t want performance-based and fixed-price contracts, and they’ve demanded that that language be taken out of the managed competition guide. And that’s one of the reasons we’re taking this to a public vote,” said DeMaio.

If the outsourcing measure makes it onto the November ballot and is approved by voters, those bidding for city contracts would not have to pay the city’s living wage of between $11 and slightly above $13 an hour.

DeMaio said his measure would save the city about $230 million, but opponents disagreed and said any savings would come at the expense of those who earn low wages already.