State officials are pressing Charles County to back off a disputed development plan they contend would degrade a vital Chesapeake Bay tributary and open up swaths of farmland to sprawling housing projects.

The heads of 13 state agencies — who make up the O'Malley administration's Smart Growth "subcabinet" — called the county's draft growth plan "unsustainable" and warned it would violate state law and jeopardize future state funding for land preservation, community revitalization and road, water and sewer projects.

The plan is to be aired at a public hearing Tuesday evening before the county's five-member Board of Commissioners.

Once completely rural, Charles County evolved over the years into a Washington-area bedroom community of just more than 150,000 people. Charles now boasts Maryland's third-highest median household income.

Advocates of the new county growth plan argue it's intended to strengthen the economy and continue long-standing land-use trends.

"I do not think there's anything wrong with that plan or with the way the county has grown," said Reuben B. Collins II, vice president of the county board, but also said he had not made up his mind about whether to vote for it or seek some changes.

Critics contend the growth plan was drawn up by development interests and would degrade the county's natural resources and worsen traffic and school overcrowding. They say Charles has the longest commutes of any county in Maryland, the highest real estate taxes outside of Baltimore, and the most portable classrooms.

"We're for growth, but smart growth," said Ulysee Davis, a retired emergency medical technician who lives in the Bryans Road area, a developing, but still rural area that the proposed plan envisions becoming a "town" one day, with 8,000 more homes. "Don't come in and push over every tree and cover up every stream, the way they have done some of these developments."

Faced by lobbying from business and development interests favoring the growth blueprint and environmental and community activists opposed to it, the county commissioners are sharply divided.

"There's a lot at stake here," said Dru Schmidt-Perkins, executive director of 1000 Friends of Maryland, a Baltimore-based group that favors land preservation and compact development.

The outcome, she predicted, could affect growth decisions statewide, as officials in other rural counties chafe at state pressure to limit low-density development, especially after a 2012 state law restricted new housing using septic systems.

State officials fired off a letter to Cecil County's executive, warning they could block major new rural housing projects there that rely on septic systems, contending that the county's new growth map doesn't comply with that 2012 law.

Cecil County Executive Tari Moore believes the letter was based on some "misinformation" and said her staff is discussing the issue with O'Malley administration officials.

The controversy in Charles County comes after more than two years of discussion and debate. A compromise plan, worked out after a series of public meetings, would have focused growth around already developed areas such as Waldorf, an unincorporated "city" like Columbia in Howard County. The blueprint scaled back development possibilities in rural areas, especially around Mattawoman Creek, which state natural resources officials have called one of the bay's best fish-spawning tributaries.

Then a group called the Balanced Growth Initiative, which includes developers and land owners, proposed the plan now up for a vote, and the county planning commission endorsed it essentially unchanged.

Among its more disputed provisions is a renewed call for construction of a cross-county "connector" highway, a project long sought by county officials but which state and federal environmental regulators ruled out because of its potential to spur more development around Mattawoman Creek. The plan also reclassifies lands now located in an "agricultural conservation" district as being "rural residential."

"They're taking their plan backward," said Richard E. Hall, state planning secretary, who was among the agency heads who signed a letter to the county last month urging the plan be changed.

Hall and the other administration officials contend the Charles growth blueprint would open up for possible development 150,000 acres that are designated by the county for farming and rural conservation. More than 300 new large housing projects on septic systems could be built, state officials contend. This would generate far more nutrient pollution to foul the bay than if the development were built in designated growth areas, where sewage could be treated in state-of-the-art wastewater treatment plants, they say.

State natural resources officials also warned that Mattawoman Creek is already beginning to degrade under development that has occurred so far.

Candice Quinn Kelly, president of the county's board of commissioners, sides with the state, calling the growth blueprint "horrible" and "frighteningly irresponsible."