The Oakland A’s, after claiming the team would privately finance its new ballpark, could receive a taxpayer subsidy worth tens of millions of dollars.

Once again, government officials are preparing to spend public money to try to keep a professional sports team under the false rationale that it would boost the local economy. We’ve seen this play before: Taxpayers are still paying off debt for stadium improvements that brought the Raiders back to Oakland in 1995.

Now the A’s are seeking a sweetheart deal to co-own and develop valuable public land at the current ballpark site to help fund their new venue six miles away. The deal is particularly underhanded, with one government agency, Alameda County, not only wasting public resources but also undermining another entity, the city of Oakland.

Taxpayers should be outraged by county supervisors’ tentative approval of the deal and by A’s President Dave Kaval’s duplicitous behavior. The deal doesn’t even guarantee that the team will complete its new ballpark and stay in Oakland.

The team has announced plans to build the ballpark at Howard Terminal, on the waterfront near Jack London Square. That makes the A’s the third professional sports team, after the Golden State Warriors and the Raiders, planning to leave the Coliseum site. And it frees up that 120-acre parcel, co-owned by the city and Alameda County, for development.

It’s prime property ripe for residential and commercial construction sandwiched between a BART station and Interstate 880. The county and the city should maximize use of, and revenue from, the parcel by widely soliciting proposals and bids from developers. They should ensure the best project for both public agencies, the neighborhood and taxpayers.

But Kaval — and city and county officials — keeps pretending that his team is entitled to cut to the front of the bidding line and develop the Coliseum land — that the A’s have some sort of inherent entitlement and social responsibility to develop the parcel.

That’s bogus. There’s no rational reason to tie those two together — except to implement Kaval’s apparent plan to reap a profit off the Coliseum property at taxpayer expense to help subsidize the new Howard Terminal park. In other words, despite his insistence that his new ballpark will be privately financed, taxpayers will pay part of the bill.

Kaval, in an interview Monday, insisted the two projects are not financially linked. But he suggested otherwise last week when urging county supervisors to approve a tentative deal to sell the county’s half-ownership in the Coliseum land to the A’s.

“We want to privately finance a new ballpark here in Oakland, and this action will go a long way in making that happen,” Kaval said.

County supervisors then voted unanimously to sign a tentative, non-binding term sheet to sell that half-ownership for $85 million. It’s a legally questionable deal at a likely deeply discounted price.

The sale would be a double-whammy for taxpayers. First, the A’s, as half-owners, would gain effective veto power over the property, limiting the city’s options — and hence reducing the market value of its share.

Second, the county never tested the market to determine the value of the property. Instead the county is relying on an appraisal to sell its half-share for $85 million.

But that appraisal was conducted as the city and county were trying to keep the Raiders from moving to Las Vegas and assumed the football team would use nearly half the site for a new stadium.

The Coliseum property is likely worth far more now that it’s all available for development. Indeed, county Supervisor Nate Miley, whose district includes the Coliseum site and who is a leading proponent of its sale to the A’s, acknowledged it could be worth $200 million to $300 million. That would make the value of the A’s half-share $100 million to $150 million, far more than the $85 million the county agreed to.

The only way to determine the true value would be to seek competitive proposals and offers for the property, says Roger Noll, a sports economist at Stanford University.

Asked if the county was selling its portion of the Coliseum site at a discount, Miley responded, “I think that would be a fair statement. But that’s offset by the fact that we’re keeping a sports team in Oakland.”

No, it’s not.

Sports teams do not pay their way, Noll says. They may enhance civic pride, but the common arguments for public subsidies “are based on the idea that a sports team is a magnet for other things. That’s the part that’s not true.”

Clearly, county officials want to extricate themselves from their partnership, more than a half-century old, with the city of Oakland managing the Coliseum site. That’s understandable — especially given the growing dysfunction in City Hall.

But shafting the taxpayers and the community in the process is the wrong way to do it.