Keppel Corp's fourth-quarter net profit plunged by 65 per cent and its full-year profit tumbled to a decade low as oil prices, which remain low, took a heavy toll.

The group cited lower contributions from its offshore marine division and made provisions for impairments.

The conglomerate's net profit fell to $143 million for the three months ended Dec 31, down from $405 million a year earlier.

Its full-year profit came in at $784 million - the lowest since 2006. Revenue for the fourth quarter dropped by 22 per cent to $1.94 billion, while full-year revenue sank by 34 per cent to $6.77 billion.

The company, whose businesses include property development and infrastructure, made provisions for impairments of $313 million in the quarter. These arose mainly from the "rightsizing" - a term used to refer to job cuts - of its Keppel Offshore & Marine unit, as well as impairments of investments and work in progress.

Excluding these impairments and provisions, its profit for the quarter was $300 million, which it said is comparable to that of the previous year.

Keppel chief executive Loh Chin Hua noted that while spending by oil majors is expected to rise, thanks to rising oil prices following Opec's landmark decision to cut output, the group does not see a quick recovery for the offshore business.

He said this business continues to be under pressure from "weak utilisation of the existing operating fleet, coupled with a supply overhang of new builds".

Earnings per share for the fourth quarter was 7.9 cents, down from 22.3 cents previously. Net asset value per share was $6.42 as of Dec 31, up from $6.13 a year earlier.

A final dividend of 12 cents per share was proposed, bringing the total dividend for the full year to 20 cents.

To maintain profitability of its offshore marine division, Mr Loh said "painful but necessary measures to rightsize the division must continue".

Despite the downturn, the offshore marine division posted a full-year net profit of $29 million. Last year, it secured new contracts worth about $500 million.

In the fourth quarter, Keppel O&M cut its workforce by 2,620 people, or about 11.8 per cent, from the previous quarter. This includes a reduction of about 1,930 in Singapore and 690 in its overseas yards.

For the full year, it reduced its workforce by about 10,600 people, or 35 per cent, of which 3,800 were based here and 6,800 overseas.

Subcontract headcount in Singapore, which has already been lowered significantly, was further reduced by about 3,300.

"We are also cutting our yard capacity and have mothballed two overseas yards. In Singapore, we are in the process of closing three yards," Mr Loh said.