Virginia Attorney General Ken Cuccinelli said Friday that critical provisions of a transportation-funding plan and a planned expansion of Medicaid are not legal, raising the possibility that two of the General Assembly's biggest achievements could be killed before they take effect.

In a legal opinion released late in the day, Cuccinelli said that lawmakers were out of line when they passed a transportation bill last month that raised the sales tax in Northern Virginia and Hampton Roads higher than the rest of the state. Residents in those two areas would pay 6 percent while most Virginians would pay 5.3 percent, but would keep the additional revenue for their own road projects.

Lawmakers wanted to raise an additional $500 million for road construction in those regions.

Cuccinelli wrote that "imposition of taxes in the specific localities constitutes a local law related to taxation prohibited" by the Constitution, though he said there were other methods that may be legal.

Cuccinelli, who is running for governor this year, is a staunch opponent of the transportation plan that would be legacy of Gov. Bob McDonnell, a fellow Republican.

The attorney general affirmed a previous ruling that lawmakers could not create a special legislative panel to trigger an expansion of Medicaid if certain reforms are met. That promised expansion would give 400,000 residents health insurance and was critical to gaining Democratic support of the transportation package.

Cuccinelli released a similar opinion last month, but most lawmakers ignored it, saying Cuccinelli hadn't even seen the bill's language and was acting merely to kill the transportation deal.

Del. Bob Marshall, R-Manassas, brought both legal questions to Cuccinelli.

The transportation plan and the budget bill are awaiting action by McDonnell, who has until the end of the day Monday to make a decision. Significant changes to either could derail the deal to raise $3.6 billion in new taxes for roadwork.