Activist investor Carl Icahn has thrown into doubt the future of a proposed $2.7bn deal by AmTrust’s CEO and his in-laws to take the firm private as he revealed a 9.4 percent holding in the firm.

The disclosure was made in a furious letter to the firm’s board accusing AmTrust boss Barry Zyskind and his wife’s family of “blatantly taking advantage” of AmTrust’s minority shareholders as they look to buy the 57 percent of the company that they do not already own.

He suggested the US insurer had cheated some shareholders out of a vote on the deal by “stealthily” deciding that shareholders of record on 5 April would be the ones to decide whether the deal should be allowed.

However, Icahn noted, AmTrust “did not bother telling shareholders or the market”.

“As a result, purchasers of the stock throughout the month of April, who rightly assumed they would be able to vote their shares, have been disenfranchised by this board,” the letter said.

“The vote scheduled for June 4, 2018 makes a travesty of the entire shareholder electoral process, and ‘shareholders’ who no longer own the shares will be voting on, and potentially deciding, our company’s future!”

The activist investor said he was speaking to lawyers as he aired his view that the vote was “absurd and devoid of fairness”.

He asked the firm to change the date of the vote signing off with the words: “Since the special meeting is just over two weeks away, time is of the essence.”

Issuing guidance on the vote, Icahn said the proposed deal undervalues the company adding that the acquisition was tabled at a time when AmTrust is underperforming both the market and its peers.

“The Icahn Participants believe that AmTrust should remain public so the public stockholders can benefit from AmTrust’s recovery or the merger consideration should be increased to better reflect AmTrust’s value.”

AmTrust’s share price closed yesterday at $13.43, just below the $13.50 offered by Zyskind and his in-laws the Karfunkel family to take the firm private.