Hundreds of tonnes of cliff face were believed to have crashed into the sea at a popular beauty spot.
The massive fall at Belle Tout, near Eastbourne, was reported to Coastguards at 3.30pm yesterday.
It happened 100m east of the Belle Tout lighthouse.
A spokesman for Solent Coastguard said the cliff face had been driven back to within a metre of a path which runs up to the lighthouse.
He said it was the responsibility of Eastbourne Borough Council to ensure signs were in place to warn people of the cliff fall and keep them away from the edge.
The lighthouse was moved 50m back in 1999, following another rockfall which left it just 12ft from the edge.
Following the move, the coastline suffered several more falls including the collapse of Devil's Chimney at Beachy Head two year's ago.
An early high tide obscured the devastation at the foot of cliffs this morning and the lighthouse appeared to be empty.
No signs had been placed along the edge of the cliff following the fall.
The only footpath affected appeared to be a private track east of the lighthouse, which at its narrowest was around 2m from the edge of the cliff.
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