British soldiers helped evacuate hundreds of people from rising floodwaters in the historic city of York on Sunday, after heavy rainfall inundated towns and cities across northern England.

Prime Minister David Cameron pledged more military help for the region as the army was deployed to move 300 to 400 people from their homes in York, where the River Ouse was expected to continue rising until Monday, the local council said.

Some 100 soldiers were also helping emergency services in the hardest hit areas of West Yorkshire, including Leeds, police said, after the region suffered its worst flooding in 70 years.

"We are dealing with an incredibly serious situation," Cameron told Sky News, after holding a conference call with ministers to discuss the emergency.

"The level of the rivers plus the level of rainfall has created an unprecedented effect and so some very serious flooding.

"We've decided to deploy more military resources, more military personnel, to help."

Up to a month's worth of rain has fallen across northern England in recent days, and flood waters have hit cities and towns including Manchester, Rochdale and Leeds.

More than a hundred flood warnings remained in place on Sunday, including 24 severe warnings, which indicate a danger to life, the government said.

Electricity North West said engineers had restored supplies to more than 18,000 customers since Saturday, but 7,524 homes in Lancashire and Greater Manchester were still without power.

Environment Secretary Elizabeth Truss said that while the worst of the rainfall had passed, there was still potential for further flooding.

"In many areas, the impact of further heavy rain falling on already saturated ground is unprecedented, with record river levels across Lancashire and Yorkshire causing flooding in upwards of 3,500 properties and the evacuation of hundreds of homes," she said.

Earlier, the Bishop of Burnley, Rt Revd Phillip North, tweeted pictures of his visit to Whalley – one of the worst affected villages in Lancashire. "Really bad in Whalley. Many driven from their homes" he said, "Keep praying."

Prime Minister David Cameron and heir to the throne Prince Charles have visited areas of Cumbria, where the floods first struck earlier this month and troops have been helping reinforce defences against rising water levels.

Accountancy firm PwC said the economic loss from the floods could be between £900 million and £1.3 billion ($1.3-1.9 billion), with the insurance industry bearing between £700 million to £1 billion of the total.

"If rain continues to fall in large quantities, and the areas with warnings in place do indeed flood significantly, it could well be that the total economic losses would breach £1.5 billion, with an additional significant increase in insurer losses from our initial estimate," said PwC's general insurance leader Mohammad Khan.