Debenhams has confirmed record annual losses and said it will close up to 50 under-performing stores.
In the year to September it lost £491.5m, against profits of £59m the year before.
The troubled department store chain, which has 166 branches, had previously said it planned to close 10 stores.
Boss Sergio Bucher said the company was “taking tough decisions” on stores where financial performance was likely to deteriorate over time.
The struggling department store chain has previously said 10 stores were earmarked for closure over the next five years but has raised that target.
The retailer’s survival plan, which was first reported by Sky News, will affect about 4,000 jobs.
About 25 store leases are due to expire over the next five years, although the company will not necessarily want to close all of those outlets.
Debenhams will have to negotiate ending other leases with landlords, many of which may be reluctant to do so given the headwinds facing retailers.
The chain has been under increased scrutiny since rival House of Fraser collapsed in August.
It said annual profits would be £33m – below previous guidance of £35m to £40m.
It has issued three profit warnings this year and shares have fallen from 35p in January to just 8.5p, valuing the company at just over £100m.