SACRAMENTO (CBS / AP) — A panel charged with reviewing plans for California’s $43 billion high-speed rail project says planners need to answer serious questions about the cost, business model and expected ridership of the system before the Legislature approves construction.

“It is no exaggeration to say that the next few months may offer the last chance for the governor and Legislature to assess and influence the overall plans for the project,” before irrevocable construction begins, says the report by the California High-Speed Rail Authority Peer Review Group.

READ MORE: Stimulus Check Latest: Is A Fourth Relief Payment Coming?

The first phase of the project is scheduled to start in September 2012 in the Central Valley. Critics want to start in more populated areas of Southern or Northern California in case the money runs out before the full system is finished.

The six-member peer review group submitted its report in response to a request from lawmakers who were concerned about a scathing May review of the project by the state Legislative Analyst’s Office. That analysis recommended lawmakers essentially suspend the project and request more spending leeway from federal officials, as well as shift responsibility for the project to the state Department of Transportation.

The group rejected both ideas but emphasized the crucial need for a detailed business plan that the California High-Speed Rail Authority is due to submit in October.

Rail authority spokesman Jeffrey Barker said Friday the agency is on track to answer all the concerns raised in the LAO’s report when it submits that plan, and that lawmakers will have ample time to review it before deciding whether to sell $10 billion in voter-approved bonds.

READ MORE: UPDATE: Mountain Lion Slips Away After Being Spotted In Backyard of Daly City Home

“We’ve been very vocal about the fact that there are huge challenges ahead for the high-speed rail project,” Barker said Friday. “We’ve said we need to advocate for more funding, we’ve talked about structural issues and the need for more staff, we’ve talked about the need to assure we have all the right tools within state government to have a public-private agency. … None of this stuff is new or shocking or we’re in disagreement with.”

The report from the six-member internal group, submitted last week, notes that later phases of the project rely almost entirely on federal, state and local money that might never materialize.

“This poses the clear risk that whatever is started will not be finished and whatever is finished may have only limited utility,” said the report.

The independent review panel of experts from transportation, business and other sectors was established as part of Proposition 1A, the 2008 voter-approved measure that authorized the state to sell bonds to begin construction of a high-speed rail line in California. The ultimate vision of the project is an 800-mile system linking the state’s major cities with trains running at up to 220 mph.

MORE NEWS: UPDATE: 'Non-Specific Threat' Shuts Down San Francisco State Campus

(Copyright 2011 by CBS San Francisco. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)