LONDON (Reuters) - Lloyd's of London insurer Lancashire Holdings beat forecasts with its first-half pretax profit as it escaped a big hit from the Gulf of Mexico oil spill, while rates for energy-sector insurance rose.

A record number of catastrophes, including the spill at oil major BP's Deepwater Horizon rig and the Chile earthquake, have hit the results of non-life insurers, along with limp investment returns.

RSA Insurance Group, the UK's largest non-life insurer, said yesterday that its first-half profit was dented by the cost of the Chile earthquake and bad weather in Europe.

But Lancashire, a Bermuda-based insurer, said it had only a modest exposure of $25 million net to the Deepwater Horizon loss, despite being one of the largest insurers of energy risks.

"We insured against the physical loss of the platform and had only de minimus exposure to the casualty side of the loss, which we believe will prove complex and expensive to resolve," chief executive Richard Brindle said.

The Deepwater Horizon oil rig explosion and oil spill has led to reinsurers bumping up their prices for offshore energy-related insurance premiums by 50 percent. Moody's estimated that the total insured loss from the worst oil spill in US history are between $1.4 billion and $3.5 billion in June.

Lloyds of London estimated the net claims from the Deepwater Horizon explosion stood at between $300 million and $600 million in June.

Lancashire reported a first-half pretax profit of $94.6 million, compared with $148.2 million in the same period last year, ahead of analysts' expectations, after it profited from better energy rates.

"The market generally feels soft outside of energy," said Jonny Creagh-Coen, head of investor relations at Lancashire.

"We've got a nice weighting towards energy, and that will come through in 2011 as the majority of the business was written before Deepwater Horizon happened, but the rate increases only came through in June and July," he added.

Lancashire said its combined ratio — a measure of profitability for insurers — was at 77.4 percent for the first half, despite the high level of catastrophe losses. A level below 100 percent indicates a profit.

"Lancashire has proved itself as a talented and highly disciplined underwriter. In H1 it proved its critics wrong by outperforming," said Christian Stobbs at KBC Peel Hunt.

Analysts expect catastrophe specialist Lancashire to be a key beneficiary in the event of a major US storm leading to harder rates this year.