Around £20m will have to be spent on the Old Severn Bridge after engineers discovered it is in a worse condition than previously feared.
£20m will be spent over the next two years to halt the corrosion
Last year, the Highways Agency spent £3m investigating the corrosion levels of the bridge's main cable suspensions.
Engineers said they have opened up a "can of worms".
They began by examining six cables, then eight and finally checked 10. All are reported to be in a worse condition than expected.
The money will be spent over the next two years to halt the deterioration.
One option which may be considered is using a dehumidifier - a solution used on the Forth Road Bridge in Scotland.
Weight restrictions may also have to be brought in for heavy goods vehicles.