LONDON (Bloomberg) ? Bermuda-based Catlin Group Ltd said its underwriting business ?performed strongly? last year and its acquisition of a rival will improve prospects.

Rates for catastrophe policies are ?robust,? while premiums for other lines are ?under pressure? this year, Catlin said in a Regulatory News Service statement yesterday.

Catlin agreed last October to buy London-based Wellington Underwriting Plc for ?591 million ($1.15 billion) to create the biggest Lloyd?s insurer. It has merged underwriting operations and expects to combine back-office platforms by the end of this month, Catlin said yesterday.

?The enlarged Catlin Group will benefit from the attractive market environment that exists in many of the specialty classes of insurance and reinsurance that we underwrite world-wide,? chief executive officer Stephen Catlin said in the statement.

Catlin said it wrote $1.4 billion of gross premiums in the first half of 2006. After the combination with Wellington, its net asset value is $1.9 billion, it said.

Shares of Catlin, which posted its statement just before today?s close of trading in London, fell 1.5 percent to 517 pence. The shares are up 4.4 percent from a year ago, lagging behind the 26 percent gain for the FTSE All-Share Nonlife Insurance Index.

Meanwhile, ratings agency A.M. Best Co. has assigned an indicative rating of ?bbb+? to the forthcoming issue of dated fixed/floating rate subordinated notes and an indicative rating of ?bbb? to the forthcoming issue of US dollar-denominated non-cumulative perpetual preferred shares to be issued by Catlin Insurance Company Limited (CICL).

These ratings are under review with negative implications, in line with CICL?s financial strength and issuer credit ratings. CICL is a wholly owned subsidiary of Bermuda-based holding company Catlin Group Limited (CGL).