Colorado's Secretary of State will investigate a complaint that Yellow Cab violated the law by trying to get drivers to lobby against a bill during the legislative session.

A complaint was filed in April against Colorado Cab Co. LLC, which does business as Yellow Cab, by Colorado Citizens for Ethics in Government.

Secretary of State Mike Coffman said Tuesday it reviewed CCEG's complaint and will investigate whether Yellow Cab or its drivers violated the law by:

•employing people who weren't registered as lobbyists to lobby against the bill

•failing to register and report as professional lobbyists

Yellow Cab has denied paying money, or giving any consideration to, a cab driver in exchange for lobbying.

CCEG, a nonprofit legal watchdog group, complained that Yellow Cab offered drivers an adjustment on the lease rate the drivers pay for the use of a cab. The adjustment would be worth between between $50 and $110. In exchange, drivers were asked to call legislators and lobby against House Bill 1114. The complaint was backed up by an affidavit of a Yellow Cab driver.

HB 1114, which the Legislature passed and which was signed into law by the governor in May, allows the Colorado Public Utilities Commission to regulate the lease rate charged to drivers. The law took effect May 30 and also appropriates money for the Department of Regulatory Agencies to regulate taxi owners and drivers.