Feb 9 (Reuters) - Loews Corp L.N on Monday reported weakness in most of its business units including its flagship insurance business due to softer underwriting which was partially offset by returns on investments.

Its insurance unit's core income decreased to $317 million in the fourth-quarter, from $342 million a year earlier, driven by lower underwriting and an unfavorable non-economic charge related to the asbestos and environmental pollution loss portfolio transfer, the company said.

Loews's net investment income rose to $714 million, from $696 million a year ago, due to higher income from fixed income securities as a result of a larger invested asset base and favorable reinvestment rates.

The company operates in insurance, energy, hospitality and packaging via units including CNA Financial CNA.N, Boardwalk Pipelines, Loews Hotels and Altium Packaging.

The New York-based company earns most of its revenue from CNA Financial, the insurance giant in which it owns a more than 90% stake, according to data compiled by LSEG.

The insurer's underlying combined ratio came in at 92.3% from 91.4%. A ratio below 100% means an insurer earned more in premiums than it paid out in claims.

Net income attributable to Loews rose to $402 million, or $1.94 per share, in the three months ended December 31, from $187 million, or 86 cents per share, a year earlier.

The year-on-year increase largely reflects a low comparison base, after results in the prior-year quarter were weighed down by a pension settlement charge of $265 million at CNA Financial CNA.N, the company said.

(Reporting by Pragyan Kalita in Bengaluru; Editing by Shailesh Kuber)

((Pragyan.Kalita@thomsonreuters.com;))