The policy committee of index provider FTSE Group is meeting Tuesday to determine whether the group should enact a minimum 25% share free-float requirement for U.K.-registered companies on its U.K. indexes, the index provider's Chief Executive Mark Makepeace said.

The meeting comes amid growing concerns that a growing number of companies have been allowed to enter the indices with free floats that are smaller than the U.K. regulatory minimum 25% free float requirement.

The FTSE policy changes are expected to be announced as early as Wednesday and would require companies that have less than a 25% free float to either raise their free float to the required threshold or lose their index status within 12 months to 24 months, two people familiar with the matter said.

The policy change would apply only to U.K.-incorporated companies listed on the FTSE All-Share index, which includes companies in the FTSE-100 index, the FTSE-250 index, and the FTSE-350 index.

The five companies that would be affected by the policy changes are Essar Energy PLC (ESSR.LN), Eurasian Natural Resources Corp PLC (ENRC.LN), Evraz Group PLC (EVRZ.LN), Fresnillo PLC (FRES.LN), and Ferrexpo PLC (FXPO.LN), the people familiar with the matter said. All of them are U.K.-listed resource companies in the FTSE 100 index and are domiciled in the United Kingdom.

Fresnillo, Ferrexpo, and ENRC declined to comment on the potential policy change. Fresnillo has a 22.9% free float, ENRC has an 18.43% free float, and Ferrexpo has around a 36% free float, according to calculations made by Dow Jones Newswires. One of Ferrexpo's shareholders, which owns a 25% stake in the company, has lent out 12% of its shares to banks for trading.

Alexander Frolov, the chief executive of Russian steelmaker Evraz, which has a 24.8% free float, said, "it's not an issue" to reach the new requirement.

A spokesman for Essar Energy, which listed in 2010 with slightly less than a 24% free float, said it would "wait and see what FTSE decides and then have internal discussions to see how we approach any new resolutions."

The potential FTSE policy change, if enacted, may do little to allay investor concerns that majority shareholders would still be able to exert significant influence over a company's strategy if desired.

"This is a half-way solution to a bigger problem with the criteria for the admission to listing regime which resides with the UKLA," said a spokesman for PIRC, a U.K. independent shareholder advisory group.

The government's U.K. Listing Authority has a 25% minimum free-float requirement for all companies seeking a premium London listing but has in recent years granted waivers to companies that have large market capitalizations.

The FTSE Group has a minimum 15% free-float requirement but is willing to consider companies with a smaller free float for inclusion in its indices if they have a free float above 5%, have been granted a waiver by the U.K. Listing Authority and have a market capitalization of more than $5 billion.

-By Alex MacDonald and Marietta Cauchi, Dow Jones Newswires; 44 20 7842 9328; alex.macdonald@dowjones.com

(Alexis Flynn in London contributed to this story.)