Google has admitted that its investment in AOL has fallen in value.

The search engine originally purchased a five percent share in the company in 2006 for $1bn (£500m), putting AOL's total worth $20bn (£10bn). However, in documents it filed with the US Securities and Exchange Commission, it said it believed the investment had depreciated and may even resort to writing off losses from the deal.

"Based on our review, we believe our investment in AOL may be impaired," Google said.

Although the search engine giant added: "After consideration of the duration of the impairment, as well as the reasons for any decline in value and the potential recovery period, we do not believe that such impairment is other-than-temporary".

See also: AOL struggles to make online ad profits