Washington ? Lawmakers and regulators are examining the fees charged by popular college-savings plans, and an investigation of big brokerage firms’ sales of the plans has widened.

An investor advocate told a House panel Wednesday that states may have incentives to sponsor so-called “529” plans with high fees and that political factors can play a role in pushing up charges.

“Political considerations … may influence the selection of money managers and cause states to be less diligent when negotiating fees,” Mercer Bullard, a University of Mississippi law professor who heads the advocacy group Fund Democracy, testified at a hearing examining the plans used by parents to save for their children’s college tuition.

Bullard cited examples of states favoring investment firms based in the state or firms whose executives contributed to the election campaigns of state officials. He urged the lawmakers to consider imposing limits on fees charged by the savings plans, which are not subject to federal income taxes and sometimes deductible from state taxes.

More than $35 billion is invested in 529 plans, which were established by Congress in 1996 and are named for the corresponding provision in the federal tax code.

At the hearing by a House Financial Services subcommittee, Rep. Michael Oxley, R-Ohio, said he had become concerned about several aspects of the plans. Oxley, who heads the full committee, said he wanted to know for example why fees differ markedly from state to state and how clearly they were disclosed.

“Have the fees charged by these state-sponsored plans become so exorbitant that they actually outstrip the tax benefits that Congress has attempted to provide?” he asked.

Securities regulators, meanwhile, have expanded their investigation of brokerage firms’ sales of these 529 plans for possible violations that can deprive investors of the very tax benefits that make the plans attractive.

The National Association of Securities Dealers has widened its examination of sales of the plans to 15 major investment firms, up from six as of March, NASD vice chairman Mary Schapiro said. She would not name the firms.

The securities industry’s self-policing organization is concerned that brokers may have sold investors out-of-state plans without clearly explaining to them that they could lose the ability to deduct their plan contributions from their state income taxes. Red flags went up, Schapiro said, when NASD examiners found that for some investment firms, more than 90 percent of sales of the plans were going to nonresidents.

“Millions of dollars are poured into 529 plans,” she said. “They’re a wonderful potential investment tool but … complicated enough that people really ought to be thinking about this.”

Brokers who recommend out-of-state plans that pay higher commissions could cost investors their in-state tax benefit, Bullard said in his congressional testimony.

The 529 plans are offered by every state and the District of Columbia. The plans usually are based principally on investments in mutual funds — an area in which the issue of fees has long been debated by policy-makers.

While mutual fund companies can raise some types of fees only with shareholders’ approval, states generally can increase fees for college savings plans without notifying investors. Some of the money from the fees goes into the coffers of states, many of which are strapped and scrounging for revenue in the current economic climate.

William Donaldson, chairman of the Securities and Exchange Commission, recently established a task force at the agency to examine the plans and how clearly the fees are disclosed.

“The current state of affairs with respect to 529 plans is complicated and likely difficult for parents to understand,” he wrote Oxley.

Richard Strong, the founder and former CEO of Strong Financial Corp., who last month agreed to a $60 million fine to settle allegations that he made improper mutual fund trades, had made campaign donations to a Wisconsin official indirectly responsible for choosing Strong’s company to manage the state’s 529 plan, Bullard noted.