An army of mentally ill homeless people have set up camp along the K Street blocks that constitute Washington's premier business district, alarming tourists and worrying business owners in the area.

"We're seeing a lot more people now," said Colleen McCarthy, a volunteer with Dorothy Day Catholic Worker, a nonprofit group that provides hot meals in McPherson Square every Thursday. "Many of them are the most mentally ill."

Some homeless advocates say the upsurge is an unintended consequence of Mayor Adrian Fenty's ambitious reform agenda. Last year, Fenty shut down the Franklin Shelter, the only downtown homeless refuge. He also had to back away from his ambitious Housing First program -- which promised to put the homeless in permanent housing -- because of a budget crunch.

"They're doing it when the wave is coming in, not going out," said Terry Lynch, spokesman for the Downtown Cluster of Congregations.

The effects have been dramatic.

"If you come through here on Saturday or Sunday, it's wall-to-wall homeless people," said Marquietta Henley, an officer with the Downtown D.C. Business Improvement District, who was herself homeless until a few months ago.

D.C.'s homeless population increased by more than 3 percent since 2005. That has crammed downtown D.C. parks with the most destitute, said Neil Donovan, executive director of the National Coalition for the Homeless.

"It's a population that's large and growing," he said.

Mayoral spokeswoman Mafara Hobson didn't respond to requests for comment. Councilman Jack Evans, D-Ward 2, who represents downtown Washington, defended the mayor's approach.

"The program that the mayor has used is absolutely the right one -- we should not be warehousing these people in these decrepit shelters. I've seen a real decrease of people out in the streets in the last two years," he said. No matter what, Evans said, "you're still going to have people out on the streets because they're resistant to outside help."

Many Washingtonians have become numb to homelessness and think little of picking their way through public parks over and around the homeless. That's part of the problem, experts say.

"Really, homelessness has become part of the public and retail space environment, much like parking meters and vending boxes and alleyways," Lynch said. "It's just part of the landscape."

Mina Naraghy, a 25-year employee of the Metro Press copying center on I Street NW, said something has got to be done.

"The city needs a homeless shelter," she said.

Many workers act pre-emptively to keep the homeless moving along.

"When we see them, we let them know right away, you can't do it here," said Victoria Mayo, a security guard at the JW Marriott hotel.

For out-of-towners, though, it's shocking to see the lost bivouacked in the shadow of the White House.

"I'm not used to seeing tents pitched in the city," said Halcion Thomas, a New Yorker traveling to Washington, as she walked through McPherson Square.

-- Examiner interns Melanie Ciarrone and Ben Giles contributed to this report.