Portland officials are recommending new regulations aimed at a private parking lot company that has been attracting criticism for its practice of booting cars and charging steep late fees.

The proposed rules will be presented Wednesday to the City Council’s Transportation, Energy and Sustainability Committee. They will include requirements for specific information on signs, including the fees for removal of a boot, a wheel-lock device that immobilizes vehicles.

The targeted company, Unified Parking Partners, has opened up thousands of parking spots in downtown Portland on nights and weekends. The company opened its first pay-and-display lot in 2014 and now manages about 40 lots and garages in Portland, including 16 pay-and-display lots downtown.

Customers who park in one of Unified’s lots prepay for the time they need, often using a kiosk that dispenses a ticket to be displayed on the car’s dashboard. Customers can use a new cellphone app to add additional parking time, but if they get back to their car more than 20 minutes late, the car is subject to booting. The fee for removing the boot ranges from $40 to $70, depending on how long the customer is overdue.

As Unified’s presence grew, criticism of its practices became more intense on social media, prompting the company to deactivate its Facebook page. At least five complaints were filed with the Better Business Bureau.

Despite the criticism, the company is not breaking any laws, city officials said. Private pay-and-display lots, which are new to Portland, are more common in larger cities, where they also generate complaints. Some communities, including Chicago, have adopted regulations for companies that boot cars, such as capping fees and requiring warning signs.

After the city of Portland received complaints about booted vehicles, the company added signs at the city’s request warning customers that enforcement action included booting, as well as a maximum fee of $70 to remove a boot, city officials said.

In a memo to transportation committee members, city attorney Danielle West-Chuhta said she was asked by several city councilors to research the city’s ability to regulate the practice of booting vehicles in private parking lots. She said the city has the authority to regulate private lots because it would be seeking to protect the safety of people and their vehicles within the city.

Under the draft ordinance recommended by city staff, Portland would require the companies to apply for a regulated business license before engaging in the practice of booting cars. The application would require companies to show proof of commercial general-liability insurance.

The city also would require the companies to display at least three signs on the property that indicate the lot is private, that vehicles are subject to booting and that there’s a fee for removing the boot.

David Farmer, a spokesman for Unified, said in an email Monday that the company is looking forward to working with the city on regulations “that are reasonable and appropriate.” Farmer said the vast majority of Unified’s customers are happy with the additional parking that the company has made available, and there have been very few complaints.

“But we also understand that with a new business innovation it can take time for people to become accustomed to it,” he said.

State Sen. Eric Brakey, a Republican from Auburn, has proposed a new state law to require companies like Unified to fully disclose the penalties for failing to comply with the rules. Brakey filed the bill last month after he was more than an hour overdue in retrieving his car from a private lot and had to pay $70 to have it released.

“You’re booting someone’s private property without explaining the terms and conditions,” Brakey said last month. “If the terms are not clearly laid out, it really strikes me as a bad business practice. If they clearly lay out the terms, then it’s buyer beware.”

Farmer said company officials have met with Brakey, as well as the city, “and believe that we are all moving forward collaboratively.”