Gov. Bob Mc­Don­nell is proposing a series of amendments to a bill that would require businesses to provide insurance coverage for children with autism.

Mc­Don­nell (R) wants to make the bill more restrictive and less costly for businesses by delaying the effective date, subjecting some treatment providers to Board of Medicine approval and tightening eligibility for some small employer groups.

The bill, passed by the General Assembly last month after 11 years of failed attempts, is strongly opposed by the business community, which considers the proposal a financial burden that companies cannot afford in tough economic times.

Legislators can accept or reject his amendments when they return to Richmond on April 6.

The bill, as passed by the General Assembly, would require health insurers to pay for a specialized therapy known as applied behavioral analysis, as well as occupational, speech and other therapies, for children ages 2 to 6. It would cap annual costs at $35,000 and apply to businesses that employ more than 50 people and are not self-insured. It would also cover public employees.

Virginia is set to join at least 23 other states that mandate insurance coverage for autism, having passed the bill with the support of House Speaker Bill Howell (R-Stafford).

But the Independent Insurance Agents of Virginia, the Virginia Chamber of Commerce, the National Federation of Independent Business and the Virginia Association of Health Plans oppose the bill and have been lobbying Mc­Don­nell to veto the measure.

The Virginia Autism Project is sending e-mails and letters and making telephone calls to urge Mc­Don­nell to keep the bill intact.

Supporters say the legislation would cost businesses less than $1 per month per autistic child and would provide medical treatment when it can do the most good. The costs are estimated to range from $590,000 to $820,000 a year.

“We have communicated with the patrons to ensure this legislation is in the proper form to guarantee the balance between meeting the needs of children with Autism Spectrum Disorders, their parents who purchase insurance coverage, businesses who provide insurance to their employees, and the industry that provides the coverage,’’ McDonnell said in a statement. “I recognize and thank those business owners who often make great sacrifices to provide affordable health care coverage to their employees. I urge my friends in the General Assembly to approve these common-sense amendments.”

This post has been updated since it was first published.