The storms that ravaged France last December cost insurance group CGNU £90 million and depressed profits in the last six months.
CGNU, the company formed by the merger in May of Norwich Union and CGU, said the impact of the storms and an increase in the number of large claims as a result had led to a "disappointing" fall in profits in its general insurance business.
Group operating profits for the six months to June 30 were £800 million, from £853 million last time, while pre-tax profits were £738 million, as against £945 million.
The storms also led to an underwriting losses in France increasing from £21 million in the 1999 half-year period to £167 million this time round.
The £41 million cost of investing in e-commerce and the £30 million cost of setting up Nowich Union International, an offshore business in Ireland, also impacted on the interim figures.
Group chief executive Bob Scott said: "Our general insurance business results were disappointing and we continue to take the necessary steps to improve profitability."
He added: "We knew we had a big belt at the end of the year from the storms, but that is the sort of thing which happens when you are in the insurance industry."
But CGNU said the integration of the two sides of the business was proceeding better than expected, with pre-tax savings now expected to be £275 million a year, not the £250 million originally forecasted.
The cost of integrating the businesses had also increased, rising from a predicted £350 million to £425 million.
CNGU also confirmed it will mean the cutting of 4,000 jobs in the UK across the group.
The group's "orphan assets" - the surplus funds built up over the years - now totalled £4 billion, said CGNU.
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