Two state Senators called for hearings Thursday to investigate whether Sound Transit misled the public about the impact of the Sound Transit 3 project and the tax package that’s paying for them.

State Sens. Steve O’Ban, R-University Place, and Dino Rossi, R-Sammamish, claim that Sound Transit tried to use an outdated method to calculate car-tab fees, was unclear about how long the project was authorized and meddled in the ST3 ballot initiative.

“We are concerned that Sound Transit may have engaged in a systematic effort to confuse and misrepresent the impact and cost of the ST3 authorization to legislators and the public,” O’Ban and Rossi wrote in a letter to Republican Sens. Curtis King and Mike Padden, who chair the Senate Transportation and Law and Justice Committees.

Related: Complete coverage on car-tab controversy

Sound Transit says it sent mailers consistent with campaign rules and were transparent about the cost throughout the whole process, through an online tax calculator and funding fact sheet.

“There is no validity to any of the claims made by the senators,” Geoff Patrick, a Sound Transit spokesman said in a statement. “Sound Transit is committed to delivering voter-approved projects and is busy doing so.”

Voters approved the $54 billion ST3 tax package last fall. Tax increases will pay to expand mass transit in King, Pierce, and Snohomish Counties with a range of light rail, commuter rail, and bus connections.

O’Ban and Rossi claim Sound Transit promoted a version of the ST3 initiative that was “unconstitutionally” drafted to use an outdated formula to calculate car-tab fees. The formula uses the Manufacturer's Suggested Retail Price (MSRP) to calculate the car's taxable value, which is often much higher than the car’s fair market value.

Related: Senate passes bill to lessen car tab taxes for Sound Transit

The Senators also claim Sound Transit may have participated in the November campaign, impacting the ST3 measure. Sound Transit increased its communications and external affairs budget by 25 percent between 2014 and 2016, coinciding with the time the legislature was considering passing the Connecting Washington package.

They also point out that Sound Transit improperly gave 173,000 ORCA cardholder email addresses to a group in favor of ST3, according to a Seattle Times report.

O’Ban and Rossi requested that either the Law and Justice Committee or Transportation Committee hold a hearing to look into their concerns.

“Even Sound Transit’s staunchest defenders are now expressing shock over how they’re pricing car-tab taxes and their overall funding authorization,” said O’Ban in a statement. “Sound Transit has had no check on its actions because its governing board members never face the voters. It’s up to the legislature to provide the oversight.”