Secretary of State Mike Coffman decided Tuesday to investigate whether Yellow Cab Co. violated lobbying laws by allegedly offering drivers new lease rates in exchange for urging lawmakers to reject a deregulation bill.

Colorado Cab Co., which does business as Yellow Cab, may have violated two provisions of the lobbying statutes, Coffman said in a letter to the Colorado Citizens for Ethics in Government, which requested an investigation March 30.

The taxi company may have employed unregistered persons to engage in lobbying, and the taxi drivers may have violated the statutes by failing to register and report as professional lobbyists, Coffman wrote.

A spokesman for Yellow Cab on Tuesday dismissed the investigation request filed by the watchdog group.

"The complaint against Yellow Cab is without merit," company spokesman Sean Duffy said. "This group has a pattern of filing frivolous actions against their political opponents, and Yellow Cab will aggressively contest this complaint and we're convinced we'll be vindicated."

Citizens for Ethics in Government requested the investigation after it obtained documents which indicated that Yellow Cab offered its drivers $50 to $110 off the lease rate they pay for use of the taxis.