The firm repeated that its huge site at Grangemouth in Scotland - at the centre of an industrial dispute with the Unite union - will close in 2017 without savings and fresh investment.
"As a consequence of the repeated annual losses by the petrochemical business at Grangemouth, the company has been required to write down the value of all of the petrochemical assets at the site, including property, plant and equipment, from £400 million to zero," said a statement.
Ineos said it had invested over £1 billion since taking over at Grangemouth in 2006 but the site lost more than £150m in the last four years.
Calum MacLean, chairman of the Grangemouth Petrochemicals Business, said: "We had no option but to write down these assets. After four years of heavy losses, the petrochemicals business is effectively worthless. Without lower costs and an alternative source of additional raw material it will close in 2017 at the latest.
"The petrochemical business at Grangemouth is at a crossroads. The current financial position is unsustainable and this write down simply confirms the stark choices that we have ahead of us."
Unite members at Grangemouth have voted in favour of industrial action and are due to start a work to rule and overtime ban next week.
The dispute centres on the treatment of union convenor Stevie Deans, who was involved in the row over the selection of a Labour candidate in Falkirk. Mr Deans, who is chairman of the constituency party, faces a probe by Ineos over issues linked to the Falkirk row.