LONDON—Omega Insurance Holdings Ltd. said Monday that it has received an unsolicited acquisition offer from Canopius Group Ltd.

Hamilton, Bermuda-based Omega said Canopius proposed an offer made up of cash and an undisclosed share consideration.

In a statement, Omega said there was no certainty that a formal offer would be made, but said it would consider any approach that would be in its shareholders’ interests.

Omega, which is listed on the London Stock Exchange, operates syndicate 958 at Lloyd’s of London and writes predominantly short-tail property insurance and reinsurance business for small to medium-size buyers.

Omega also operates a U.S. specialty reinsurance company—Schaumburg, Ill.-based Omega U.S. Insurance Inc. —and a Cologne, Germany-based coverholder, Omega Europe GmbH.

Last week, Omega said it had increased its estimate of losses from the September earthquake in New Zealand to about $18.9 million from its previous estimate of $7.0 million. It said the increase came after several primary insurers and reinsurers for which its writes retrocessional cover had increased their loss estimates in recent weeks.

Omega noted it was too early to give any estimate of potential losses from the current floods in Queensland, Australia.

For the first nine months of 2010, Omega had gross written premiums of $308.5 million.

Guernsey-based Canopius manages syndicates 4444 and 260 at Lloyd’s of London. It also has a specialty lines company that underwrites on behalf of syndicate 4444, and runs syndicate 839.

Canopius, which has operations in Australia, Bermuda, Ireland, Singapore and the United Kingdom, last week said it had established a European reinsurance underwriting platform in Zurich.

Canopius Europe, which will focus initially on European treaty reinsurance and underwrite on behalf of syndicate 4444, is slated to begin operations in mid-2011, subject to regulatory approval, the company said in a statement.

The operation will be headed by Eric Gutiérrez, now senior vp of ACE Tempest Re International and general manager of ACE Reinsurance (Switzerland) Ltd.

For 2009, Canopius posted a pretax profit of £55 million ($85.5 million) and gross written premiums of £592 million ($920.4 million).