Major automakers broadened their objections on Thursday to proposed U.S. auto safety legislation, including one provision they say could trigger more lawsuits.

Parts companies, dealers and the U.S. Chamber of Commerce, a leading business lobby, also joined the Alliance of Automobile Manufacturers in registering fresh opposition to several provisions.

With Congress facing a number of priorities and a tight time schedule this summer and fall, it is unclear when the bill, spurred by major recalls by Toyota Motor Corp, would be considered by the full House of Representatives and Senate.

Committees in both chambers have approved separate versions of the most sweeping attempt to update car safety laws since legislation following the Firestone tire debacle nearly 10 years ago.

The new legislation seeks to sharply increase fines for violating federal safety disclosure regulations, impose standards for new vehicle technology, and give additional authority to regulators.

Automakers have spoken out against increasing fines and removing caps on them as well as proposals to force certain vehicle design changes that would raise costs and potentially slow production and sales.

But industry on Thursday stiffened its objections to other issues.

Automakers, in a letter to key House and Senate members, spoke out against a proposal to permit court appeals when regulators reject consumer petitions to investigate defects. They argue this provision has already been addressed by the courts and could slow recalls, which in most cases are negotiated with regulators and carried out voluntarily.

They also objected to a plan that would expand public accessibility to industry safety data, and another that would hold senior car company executives more accountable for proper disclosure of safety issues. Automakers favor placing responsibility with a designated company safety official, rather than an officer.

(Reporting by John Crawley; Editing by Steve Orlofsky)