Pension SuperFund Capital has reported an “inadvertent breach” of one of the rules of City Code on Takeovers and Mergers in its announcement on 8 September about its offer for SIPP provider STM Group.

As a result, it said it has released Clifton Participations Limited from undertakings on 2 million shares.

The undertaking has now been replaced by a letter of intent to support the transaction.

The company’s £39m bid for STM Group was extended for a fourth time on 8 September.

The current deadline is 5 pm on 27 September with Pension SuperFund Capital having until then to confirm its offer or withdraw.

STM said: “There can be no certainty that any offer will ultimately be made for the company.”

It also revealed that its nominated adviser and broker, finnCap Ltd, has now changed its name to Cavendish Capital Markets Ltd.

So far 32.7% of STM Group shareholders have indicated they would vote in favour of a 67p a share offer for the business if it goes ahead.

Among a number of UK and European interests, STM Group owns Options Pensions and London & Colonial Pensions.