A group of investors who advise the U.S. Securities and Exchange Commission on market rules said the regulator should drop plans to test new incentives that would encourage trading in small-company stocks.

The SEC’s Investor Advisory Committee is meeting today to recommend the agency not conduct a pilot program to widen the minimum price, or tick, at which small stocks are quoted on exchanges. The trial program, which has supporters in Congress, would reward brokers for making markets in less liquid stocks by widening the spread they earn when buying and selling shares.

“We are concerned that any increase in minimum tick size would disproportionately harm retail investors, who would see their trading costs artificially inflated above the rate set in competitive markets,” the committee wrote in the recommendation to be voted on today.

Some of the program’s supporters say wider tick sizes would promote trading in less liquid stocks and encourage more companies to go public. The SEC required all stocks to be priced in penny increments in 2001, after more than 200 years during which stocks were priced in fractions.

The advisory committee’s opinion is unlikely to stop plans for a tick-size pilot but could affect how regulators design it. SEC Chairman Mary Jo White said in October the SEC was moving forward with plans to develop the trial program. The House Financial Services Committee advanced legislation in November that would force the SEC to establish such a pilot.

“There is quite a lot of activity going on both in the industry and at the SEC” on a tick-size pilot program, SEC Associate Director Gregg E. Berman said yesterday at a Brookings Institution event. “We have been doing a lot of preparatory work to try to measure what the effect might be.”