Sky News understands that Pension Superfund Capital, a vehicle controlled by Edi Truell, is among a number of parties to have indicated that it wants to make an offer for the company.

City sources said the approach from Pension Superfund Capital was likely to be disclosed in an announcement on Tuesday morning.

An insider connected to another party which had expressed recent interest in STM said that finnCap, the investment bank, was advising the pension master trust on the talks.

Although a stock market minnow with a market capitalisation of little more than £15m, STM is understood to have been identified by Mr Truell as a platform to deliver a comprehensive range of pensions services to clients.

The entrepreneur, who recently took Global Interconnection Group, an energy transmission business, public in Amsterdam, is a veteran of pensions industry innovation.

He helped establish Pension Insurance Corporation, the specialist insurer, and was the architect of the Pension Superfund, one of a new breed of consolidators which has been attempting to gain regulatory approval.

Mr Truell's move also comes as the chancellor, Jeremy Hunt, unveils sweeping reforms to the way Britain's pensions industry operates.

Shares in STM closed on Monday at 27.5p, having risen by 17% during the last year.

Neither Pension Superfund Capital nor STM would comment on Monday.