The secretary of state has certified a referendum for the November ballot that will ask voters to repeal California's controversial new law requiring companies to buy health insurance for workers, backers of the referendum effort announced Monday.

Official certification of the more than 624,000 petition signatures submitted will allow opponents of the new law, a coalition of business groups called Californians Against Government Run Healthcare, to put their referendum on the ballot.

The law, SB 2 by Senate President Pro Tem John Burton, was signed by Gov. Gray Davis just before the recall election that removed him from office.

Backed by a broad coalition of labor, consumer and doctor groups, SB 2 requires companies with 200 or more employees to buy health insurance for workers and their families by 2006. Firms with 50 to 199 employees would need to purchase coverage for workers by 2007.

Supporters said the law would extend coverage to well over 1 million uninsured workers and their families at a cost to employers of no more than $1.5 billion in premiums.

Businesses bitterly opposed the measure, which they estimated would cost firms as much as $11.5 billion, and started efforts to repeal the law as soon as Davis signed it.