Network rail has apologised for any disruption the track closures cause

From Sunday, 24 December, no trains will operate in Portsmouth until 5 February, 2007.

Buses will also replace trains on the lines from Portsmouth Harbour to Petersfield, Fareham and Chichester as the lines close until 2 January.

Network Rail says the signalling overhaul on the 50-mile track section will allow for more reliable journeys.

David Pape, the company's route director, said: "The final phase of this enormous project brings us one step closer to delivering better, smoother and more reliable journeys for passengers."

I believe the long term benefits for passengers will make this additional work worthwhile David Pape, Network Rail

On 14, 27 and 28 January, the tracks will be closed from Portsmouth Harbour to Petersfield, Fareham and Chichester and again from 1 February to 4 February.

On Sunday, 4 February, the closure will extend to between Portsmouth Harbour and Haselmere, Swanwick and Eastleigh.

Mark Dunn, of South West Trains admitted that the next few weeks would be challenging.

'Signalling benefits'

"Our highest priority is ensuring our customers can still make their journeys as quickly as they possibly can," he said.

Network rail has apologised for any disruption caused.

Mr Pape added: "Our focus is to complete works on schedule so that passengers can experience the benefits of the new signalling equipment straight away.

"I believe the long term benefits for passengers will make this additional work worthwhile."