The firm said up to 15 per cent of the 1,300 businesses on Aim would be lured to the main market by the attraction of a standard listing option, which will offer lighter regulation than the premium route.
While standard entrants will still have to register with the Financial Services Authority, corporate governance disclosures are expected to be less onerous.
Seymour Pierce, which acts as an adviser to smaller companies, said: “The inability of Aim to fulfil its objective as a market for new growth stocks to obtain funding will come under further threat… The potentially lower listing standards of the lower tier are likely to attract both existing stocks and new market entrants.”
The LSE pointed out Aim had managed to attract a large number of international companies over the years, even though the standard listing has already been available to overseas firms.
A spokesperson added: “The standard listing will give an extra choice for companies somewhere between Aim and the premium listing.”