The company said that it had recently received a "number of requests" to raise its free float requirement for listing from the current 15% to 25% of a company's total share capital.
A company's 'free float' is the percentage of its shares that are held by investors who are likely to be willing to trade them. It therefore excludes those shares held by 'strategic' shareholders, such as parent companies and company directors.
The Financial Services Authority (FSA), acting in its role as the UK Listing Authority (UKLA), already requires companies wishing to obtain a 'premium' listing on the London Stock Exchange to have a minimum free float of 25%, however it can grant exceptions to this requirement. FTSE said it would also consult on whether an exemption to any new requirement of its own should also be granted if the FSA had already done so.
Companies with a premium listing are required to meet the UK's 'super-equivalent' rules, which are higher than the EU minimum requirements.
The change would only apply to UK incorporated companies. Companies incorporated outside of the UK are already subject to a higher free float threshold of 50%, FTSE said.
A UK incorporated company must currently have a minimum free float of 15% of its total share capital to be eligible for listing on either the FTSE UK Index Series or the FTSE Global Equity Index Series. However, companies with a value of more than $5 billion can have a free float of as low as 5% in certain circumstances.
Press reports have suggested that investors are becoming wary of increasing numbers of Russian companies looking for listing on the London Stock Exchange with only small amounts of available shares.
"Some investors have become wary of these types of companies as they have large founder-shareholders that can dominate the business," said a report in the Telegraph.
The consultation also asks whether FTSE should consider creating a new set of indices which would "impose a higher standard of corporate governance".
FTSE said the results of the consultation and any proposed changes to the rules would be presented to its Policy Group in December. Any FTSE All-Share stocks which do not currently meet the requirement will be grandfathered, giving them time to increase their free float, it said.
