In a blistering three-page letter citing “numerous misrepresentations of material fact,” the San Francisco Recreation and Park Department denied a permit for a free Summer of Love 50th anniversary concert to be held June 4 at the Polo Field in Golden Gate Park.

Event promoter Boots Hughston was sent a rejection letter Tuesday, less than two weeks after he had made a public announcement about the concert, telling The Chronicle that the city department had given him the date and go-ahead for the event, with a permit all but assured.

In her letter, Diane Rea, manager of permits and reservations for Rec and Park, stated that after nine months of work, Hughston had still failed to supply adequate information about how security and crowd control would be handled.

Rea also questioned the anticipated size of the audience, stating that while Hughston had repeatedly told the department that the crowd would be no more than 30,000 or 40,000, he had advertised online that the event would attract a crowd of 80,000 to 175,000.

“You have made numerous representations about your preparedness for this event which have turned out to be untrue, and if left unchecked, could put the public at risk,” Rea stated.

When reached by phone at his Mill Valley home Wednesday, Hughston said that he has subsequently met all of these demands and followed up with the city department — which, he added, has ignored his responses. Hughston said he is considering taking legal action against the city.

“This is a character assassination on me all the way down the line,” said Hughston, 68, who claims a long history of putting on peaceful free tribute concerts in Golden Gate Park. Among these were a Chet Helms memorial in 2005 and a 40th anniversary Summer of Love concert in Speedway Meadow, for which he had a permit. The crowd was estimated at 50,000 and there was no mention of arrests or trouble, according to a Chronicle report.

“I’ve been doing shows for 40 years, and they’re acting like I’ve never done anything,” Hughston said.

Rea complained that in response to Hughston’s pledge that free medical services would be provided and that adequate security had been lined up, the department reached out to the providers he cited, but they denied any such deal.

In one example, she wrote that Rock Medicine had not agreed to donate services and when contacted “they told us they had never heard of you.” But Gordon Oldham, director of Rock Medicine, said Wednesday that while he did not yet have a contract with Hughston, Rea’s claim was not a concern.

“We support the Summer of Love 100 percent,” Oldham said. Furthermore, he added that when contacted by city officials “there was no asking me if I knew Boots or any of that. I know Boots. That I can tell you.”

The golden anniversary concert was to have been a major focal point of a Summer of Love celebration that involves all the major museums and cultural institutions in San Francisco and Berkeley.

Hughston said he’d lined up Eric Burdon and War, the original rhythm section of the Santana Blues Band, and Country Joe McDonald, as well as remnants of the Jefferson Airplane/Starship, Moby Grape, Sons of Champlin and the Youngbloods.

“The Summer of Love was a cultural event that changed the world,” Hughston said, “so for them to want to stop it blows my mind.”

Country Joe McDonald had not heard about the permit denial, but was not surprised by the news.

“It’s the Summer of Money,” McDonald said. “I’m sure if Boots could pay the amount of money that Outside Lands gives the city he would have the permit in his hands right now.”

Outside Lands, the mega music festival produced by Another Planet Entertainment and Superfly Productions, paid the city more than $3 million for its music festival in the park last year, according to Rec and Park. Hardly Strictly Bluegrass, a free festival, paid $176,000 — but it does not use the Polo Field, an athletic field that requires extra care.

Hughston, a real estate flipper with holdings in San Francisco and Portland, Ore., said he plans to pay for the event out of pocket and has $700,000 budgeted. This includes fees requested by the city department for $38,000 per day for three days, plus a $50,000 fee to cover damage to the grass and $50,000 for staff, for a total of $214,000.

But Sarah Madland, director of policy and public affairs for Rec and Park, said money was never an issue.

Hughston plans to appeal the permit denial to the full Rec and Park Commission.

“I don’t get it,” he said. “I have never had a problem in the park.”

Sam Whiting is a San Francisco Chronicle staff writer. Email: swhiting@sfchronicle.com Instagram: @sfchronicle_art