The London Stock Exchange has raised concerns with the City regulator about potential “market abuse” from some bulletin board users and social media influencers as part of its attempts to improve the appeal of the junior market.

Bosses at the exchange have also been alerted to companies on the Alternative Investment Market (Aim) being “subjected to unacceptable public abuse” that is said to be acting as a disincentive for other companies and directors to float. The LSE plans to make “detailed referrals” of incidents to enforcement agencies and is encouraging companies to do the same, “so that the pattern of conduct becomes indisputable”.

The plans form part of a response to a discussion paper on “shaping the future of Aim” as the LSE seeks to lift the market, which had its 30th anniversary this year. There has been a downturn in flotations recently and a trend of listed companies going private.

The number of companies listed on Aim has fallen from a peak of 1,694 in 2007, before the financial crisis, to 625 this year. New listings have fallen from a high of 519 in 2005 to 17 this year.

The exchange’s review concluded that market responses showed the “strength of feeling and support for Aim, a market uniquely positioned between the private markets and the main market” and the “vital social and economic function Aim performs … to support the next generation of growth companies”.

However, it is planning to make changes, including “encouraging a founder-friendly environment”.

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A lack of access to “high quality” research on smaller companies for investors has in some cases created a “vacuum which is filled by bulletin board users”. While many act responsibly and in compliance with UK law, there are cases where companies, directors and nominated advisers are inappropriately targeted to seek to influence share prices.

The LSE said: “We have been discussing with the Financial Conduct Authority our concerns in respect of the conduct of certain platforms, social media influencers and bulletin board users and have highlighted potential cases that give rise to concerns of market abuse.

“We would encourage companies, market practitioners and bulletin board users who have reasonable cause for concern of this type of behaviour to report matters.

“The FCA has confirmed that posting information which gives, or is likely to give, a false or misleading impression about an issuer — where the person knew or should have known this would be the case — may constitute a breach of UK MAR [market abuse regulation]. This applies to both positive and negative statements.”

Some companies believe the “unacceptable public abuse” from bulletin board users is unlikely to occur in private markets.

“The feedback is that this is a disincentive for companies and individual directors to join Aim,” the exchange said. “We consider it is unacceptable for Aim companies and directors to be exposed to such pressure.”

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The strongly worded report did not name specific bulletin boards or companies and the exchange declined to provide further details.

Charles Hall, head of research at Peel Hunt, the City investment bank, said: “Bulletin boards are the wild west of investing. The ability to be anonymous, to post misleading, abusive or incorrect commentary damages trust in public markets and needs to be addressed. Confidence in markets is essential, particularly as the government is encouraging savers to invest in stocks and shares.”

A spokesman for the FCA said: “Regardless of the way in which it has been done if someone knowingly shares false or misleading information about a publicly traded company, they’re potentially breaking the law.”