Fire crews have been called to a fire at Brunel House, opposite Gunwharf Quays.
Crews from Southsea and Cosham are dealing with the fire on one of the lower levels of the tall building, opposite the entrance to Gunwharf.
The fire in the derelict building was reported at 4pm today.
The road was closed by police while emergency services dealt with the fire.
The plans caused controversy last year after the developer revealed it would be ‘unviable’ for social housing to be included in the proposals, much to the dismay of Portsmouth Tory planning boss Luke Stubbs.