The director of Southern California's major water wholesaler defended his agency's drought plan in the face of a lawsuit that alleges the plan overcharges poor customers to subsidize new development in affluent areas.

Metropolitan Water District general manager Jeff Kightlinger said the plan being challenged by the Central Basin Municipal Water District in southwest Los Angeles County treats all customers equally.

"It treats people in Beverly Hills the same way it treats people in Compton, Riverside, Orange County," he said.

The MWD approved the allocation plan in February in preparation for a possible worsening of current water shortages.

The agency has cut water deliveries across the board during previous droughts. But the new plan sets a formula for determining how imported water would be divided that allows cities to receive more water if they are in growing counties, among other situations.

The lawsuit, filed in Los Angeles County Superior Court, contends the plan unfairly penalizes the Central Basin's lower-income, largely Hispanic communities while benefiting growing inland areas.

The complaint alleges the plan would give "'cheap' water to growing, more affluent water districts and communities, at the expense of poorer water districts and communities."

It also contends the MWD board did not perform required state environmental reviews and ignored water rights that favor older southeast Los Angeles County cities.