(Adds detail on results, background) Feb 18 (Reuters) -...

(Adds detail on results, background)

Feb 18 (Reuters) - Australia's Woodside Petroleum (WPL) on Thursday posted a 58% slump in annual underlying profit, highlighting a year marked by huge asset writedowns as a result of lower demand for oil and gas because of the COVID-19 pandemic.

The country's top independent gas producer reported underlying net profit after tax, which excludes one-time charges, of $447 million, compared with $1.06 billion a year ago. It missed the Refinitiv estimate of $530 million.

Like its peers last year, Woodside was hammered by a near-collapse in oil and gas prices due to the pandemic, which led the company to halve its planned spending and defer decisions on its two biggest gas projects.

In its half-year results, the company took an asset write-down of $4.37 billion after tax, joining global energy majors such as BP BP.L and Royal Dutch Shell RDSa.L that had to slash the value of their assets.

Woodside said that its $11 billion Scarborough project was on track for a targeted final investment division in the second half.

Woodside stuck to its forecast for fiscal 2021 output of 90-95 million barrels of oil equivalent, lower than its production in 2020.

On a statutory basis, Woodside posted an annual loss of $4.03 billion, its first loss in eighteen years.

It declared a final dividend of 12 U.S. cents per share, down from 55 U.S. cents paid last year.