GM claims the language aims to block 'fly-by-night' companies that can't afford liability lawsuits, but it explicitly limits autonomous testing to vehicle manufacturers.

Draft legislation created with input from General Motors could ban autonomous vehicle testing by Silicon Valley disruptors and other startups that aren't established automakers.

The 'Safe Autonomous Vehicle' bills, under consideration in several states, would only allow established automakers to operate fleets of prototype autonomous vehicles, according to an Automotive News report.

Ride-hailing companies, Google's Waymo, suppliers and many other small companies are currently operating small fleets of experimental vehicles. As of early February, California's DMV has granted testing permits to 22 different companies; less than half are current or prospective automakers.

"This kind of anti-competitive bill will only slow down the rollout of live-saving technology and create an unlevel playing field at the expense of consumer safety," Waymo said in a statement.

Waymo and Uber have succeeded in pressuring Michigan state legislators to broaden the language before the bill was signed into law, but the narrower wording is said to be contained in parallel legislation under review in Tennessee, Georgia, Maryland and Illinois.

Other opponents suggest state-level legislation should be entirely avoided, allowing the federal government to implement a standardized system for the entire country. Despite apparently supporting a patchwork of new state bills, GM is also part of a lobbying effort focused on changing federal laws to clear the way for self-driving vehicles.