Billionaire biotech investor Carl Icahn has criticised the management at Biogen Idec, in which he has a small stake, for their inability to find a buyer for the firm.

His criticisms were disclosed in a regulatory filing to the US Securities and Exchange Commission and relate to Biogen’s decision to take down the ‘for sale’ sign last month after no serious offers were made. At the time, the biotechnology giant said that it conducted “a comprehensive and thorough sale process” with financial advisors Goldman Sachs and Merrill Lynch but had decided to remain independent.

That decision did not please investors, not least Mr Icahn. In the filing, he states that ”Biogen's recent purported attempt to find a suitor was not conducted in a way to enhance the success of the endeavour''. He adds that “we believe the process was flawed in a number of key respects and that the process was run to placate us and other large shareholders.''

Specifically Mr Icahn claims that Biogen’s refusal to let bidders talk to Elan Corp, its co-partner for the multiple sclerosis drug Tysabri (natalizumab) scuppered any chance of a sale. He says that the firm’s confidentiality agreement was so restrictive that it prevented potential acquirers from bidding.

Now, in an attempt to get more influence when it comes to future decision-making, the billionaire’s Icahn Partners group has put forward three nominees to stand for election to the Biogen board. It currently has 12 members, four of whom up for election this year, and Mr Icahn is also proposed a change in the firm’s bylaws to permanently set the size of the board at 12.

Biogen said it will review Mr Icahn's notice and “consider it in light of the best interests of all shareholders”. The high-profile investor currently holds a 4.2% stake in the firm, considerably less than his holding at ImClone Systems where he is chairman but analysts believe he is unlikely to get anything like as much influence at Biogen.