BOSTON — The operators of one of Boston’s largest taxi companies have sued the developer of a smartphone app that allows users to request a cab or livery service, saying it is essentially an unlicensed car service.

A lawyer for Boston Cab Dispatch Inc. and EJT Management, which combined have about 500 taxi licenses under the Boston Cab brand, says the Uber Technologies Inc. app ignores virtually all government rules in place for cab companies.

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In the suit, Boston cab operators said the private cars available through Uber are allowed to choose among their customers and destinations, unlike cabbies, prohibited from refusing to take fares based on age, disability, and location.

Uber had no comment on the lawsuit, but a manager tells The Boston Globe the company operates legally in Massachusetts.