A US-based asset management firm yesterday slammed the board of takeover target PartnerRe for their handling of a bid by Italian investment giants Exor.

And Tom Sandell, the CEO of Sandell Asset Management, has written to PartnerRe chairman Jean-Paul Montupet accusing the firm of not acting in the best interests of shareholders by backing a plan to amalgamate with insurance and reinsurance firm Axis.

Exor has offered $6.8 billion in cash for PartnerRe, against an all-share $11 billion merger proposal by Axis.

Mr Sandell said that PartnerRe’s refusal to give Exor a list of preferred shareholders, who make up around 40 per cent of the shareholder vote, was “unreasonable”.

Mr Sandell added: “We believe the board is doing this in order to protect the Axis transaction in disregard of the shareholders’ best interests.

“We find this action egregious in today’s corporate environment of increased shareholder engagement and to constitute an international failure to conform to current corporate best practices.

“This conduct is particularly outrageous in light of Exor’s improved and superior offer which includes, among other things a 100 basis points increase in dividends for PartnerRe shareholders, call protection until 2021 and five years of capital distribution limits.”

And he said: “We fail to understand how the board’s refusal to disclose to Exor the identity of PartnerRe’s preferred shareholders so that Exor could directly contact such holders in order to fairly allow them to consider the Exor offer is consistent with your fiduciary duties to such shareholders and the board’s stated desire to maximise value for all shareholders.

“We strongly urge the board to release this information to Exor.”

Mr Sandell, whose firm has a holding of around one per cent in PartnerRe, added: “While we continue to understand the importance of maintaining a cordial relationship with Axis, we would once again like to remind the board that its first and foremost duty is to the company’s shareholders, its true owners, who should be given the simple opportunity to fairly evaluate all legitimate strategic alternatives presented.”

And he said: “Consistent with out own duties to our investors, we will not hesitate to exercise the rights available to us to hold the board accountable.”

Exor, which has built up a 9.9 per cent share in PartnerRe, making it the biggest single shareholder, said it intended to retain PartnerRe as a stand-alone company and keep existing management and staff.

The Axis-PartnerRe deal would create the world’s fifth largest reinsurer and the two companies have said joining forces would save $200 million a year — with some of the savings from redundancies among the combined Bermuda-based staff of around 130.

And the two reinsurance firms — near-neighbours on Pitts Bay Road in Pembroke — would also probably require less office space.