Poole’s Twin Sails Bridge is expected to remain raised and the road closed to all traffic until mid-June.
The bridge was taken out of action on May 17 for engineering inspection work.
BCP Council say additional investigation and remedial works are now required before returning it to operation.
It’s apologised for the inconvenience caused.
In a statement, Cllr Andy Hadley, BCP Council Portfolio Holder for Climate Response, Environment and Energy said: “A further review of Twin Sails Bridge has unfortunately shown that additional investigation and remedial works are required before returning it to operation.
“Our teams are working hard to get it operational as soon as possible, but we anticipate that the bridge will remain in the raised position with the road closed to all traffic until mid-June.
“Whilst safety must be our priority, we do understand the impact that this will have on users of the bridge, and we apologise for the inconvenience caused.
“We are reviewing the lifting timetable for Poole Bridge with the Harbour Commissioner to reduce the impact on traffic, and the signals on Blandford Road have been adjusted to allow continual flow on the main road.”