The blueprint for a major medical and life sciences research hub in the White Oak section of eastern Montgomery County has been bounced back to the Planning Board by the County Council, which says that proposed road and transportation improvements are inadequate to handle traffic generated by the new construction.

The White Oak Science Gateway Master Plan, approved by the Planning Board on Sept. 19, calls for 4 million square feet of new commercial and residential development in its first phase and 11 million overall. Its centerpiece, LifeSci Village, is a joint venture of the county government and Percontee, a private developer. Officials envision the project, bolstered by the neighboring U.S. Food and Drug Administration headquarters, as a major new employment center for Montgomery’s economically lagging eastern end, creating as many as 10,000 new jobs.

But the project could also worsen already crushing traffic along Route 29 and New Hampshire Avenue, much of it from Howard and Prince George’s counties.

“The draft plan is not in balance between land use and transportation,” Council President Nancy Navarro (D-Mid-County) told Planning Board Chair Francoise Carrier in a letter Wednesday.

County planning staff acknowledged the issue in the draft submitted to the council last month. It said that traditional methods for achieving balance — decreasing the scale of construction or building new roads — were not possible in the eastern county. Even with a proposed bus rapid transit network and a series of elevated interchanges along Route 29, balance was not possible, according to the draft.

Planners also said that decreasing the size of the project would make it more difficult to extend mass transit into the area “or spur the kind of reinvestment many community members seek and that the county has already established as an important public policy.”

Over the summer, representatives of Percontee and County Executive Isiah Leggett told the Planning Board that transportation infrastructure costs made the project financially unfeasible. They asked that traditional methods of forecasting traffic be set aside for “alternative approaches.”

Among these would be a requirement that 30 percent of the trips to new buildings on the site be made without cars.

The plan also called for a technical working group that would convene after council action to work out the details of an alternative implementation system.

But Navarro said it was the consensus of the council members she consulted that this was the board’s job, not the council’s. It was unclear how long it would take to find a palatable solution or how long that would delay the project.

“We believe that this work should continue under the aegis of the Planning Board so that the Council will have the full package of recommendations when it takes up the plan,” she said. “We cannot approve the zoning without a full understanding of how the proposed transportation system will work.”

Carrier, who presided over a day-long planning board session Thursday, could not be reached to comment.

A public hearing the council had set for Oct. 29 will be rescheduled, Navarro said.