Heavy rain has returned to flood-ravaged Cumbria as fears grew over the future of a key bridge.

Up to 3.9in (100mm) of rain is predicted to fall on parts of Cumbria's already-saturated ground, raising river levels and putting the emergency services on flood alert throughout the day.

Cumbria County Council said Calva Bridge, which has been declared unsafe and carries a number of cables, dropped several inches.

It warned Workington residents that if it collapses, 1,000 homes north of the river will lose their telephone connections.

The scene after a bridge over the River Derwent collapsed in Workington Full Image

But the Environment Agency said that although heavy rainfall was predicted across the county, river levels were not expected to be as high as when the deluge began last Thursday, with some parts of Cumbria seeing more than 12in (305mm) in 24 hours. Six bridges have already collapsed, causing major transport and logistical headaches for thousands of people.

Meanwhile, David Cameron visited the Cumbrian town of Cockermouth and witnessed the devastation caused by "a flood of biblical proportions". Following a tour around the Fire and Rescue headquarters in the town the Tory leader pledged to "fully support" the flood-hit community if his party won the next general election.

He said: "The cost of restoring some of these bridges and securing the infrastructure is going to come into the millions of pounds and they are going to need help, and central government needs to provide that help."

Mr Cameron visited Christ Church in Cockermouth before walking down Main Street with the Chief Constable of Cumbria Police, Craig Mackey, where hundreds of homes and businesses have been seriously damaged by floodwater.

He said: "Obviously these were completely horrific floods. When you walk down Main Street in Cockermouth you can just see that it was a flood of biblical proportions and there wasn't any set of flood defences that could have really withstood what happened."

The Tory leader said: "But the most overwhelming sense you get today, a few days afterwards, is just this incredible community spirit of people coming together, helping each other and working together to sort through these problems and to try to get their lives back together and it's truly impressive and humbling to see."