Gov. Scott Walker's collective bargaining proposal could force the city of Madison to restructure Metro Transit or lose $7.1 million in federal transit aid, about a sixth of the utility's $42.4 million budget for 2011, officials said.

"I'm very concerned," Mayor Dave Cieslewicz said Thursday. "If you could imagine cutting one sixth of service, that would be a disaster."

It's still unclear when the city might lose the money if the proposal is enacted, Cieslewicz said.

The governor's legislation would effectively strip most collective bargaining rights from most public workers in Wisconsin, including those working for local governments.

But federal law requires continuation of collective bargaining rights on wages, pensions, working conditions and other conditions to get federal transit money, according to a Legislative Fiscal Bureau memo.

The Walker administration did not respond to a phone call and e-mail.

The state received $73.9 million in federal transit funding in 2010, including $22.5 million for the Milwaukee area and the $7.1 million for Madison, according to the memo.