Ministers have been accused of failing flood-stricken communities in the north-west of England, after Labour highlighted a £115m fall in spending on risk management and defences this year.

Liz Truss, the environment secretary, defended the current level of spending as she was repeatedly pressed by MPs in the Commons about the impact of budget cuts. But she promised to review the “way we invest in flood defences” in light of the latest floods to hit Cumbria and Lancashire.

Many of the flooded areas were supposedly protected by defences, but these were overtopped because rainfall exceeded all previous records.

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Truss said a record £2.3bn was being spent on new defences over the next six years and promised that the annual £171m budget for maintaining current safeguards would be protected in real terms over the parliament.

However, Labour pointed out the overall flood and coastal erosion management budget of £695m was 14% lower than last year, when funding peaked after the extreme weather of winter 2013. It is also still lower in real terms than it was in 2009 and 2010, when funding for flood management was slashed under the coalition.

Kerry McCarthy, the shadow environment secretary, said these previous cuts had left the UK “unprepared for extreme weather events”, and she accused the prime minister of breaking promises about flood protections.

“It is not enough for David Cameron to promise that money is no object after serious floods happen,” she said. “Under his watch £115m has been cut from flood management in the past year. The government needs to do everything it can to protect people’s homes and businesses before flooding occurs.”

Truss highlighted the unprecedented nature of the rainfall that has caused the flooding in Cumbria and Lancashire. She said: “Climate change is factored into all the modelling work the Environment Agency does but clearly in the light of this extreme weather we are going to have a look at that modelling and make sure it’s fit for purpose for future decisions.”

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She added: “We constantly review the way we look at the way we invest in flood defences. My view is it’s really important that we remain fair to people right across the country, and the people of Cumbria understand why those decisions are being made and also get the proper protection that they deserve.”

The government is reviewing its flood risk data after repeated extreme weather events of the kind that supposedly should occur only once in many decades.

The prime minister’s spokeswoman said after an emergency Cobra meeting that the unprecedented water levels had led to flood defences being overtopped. “There was an agreement that the government should look again at the level of rainfall we have seen in the floods, and how that tallies with the flood defences,” she said

Cameron visited Carlisle where he said the damage was “absolutely horrific, and it’s not the first time it’s happened, which is why we built these defences”.

He said councils would be fully reimbursed for the costs of dealing with the floods under the Bellwin scheme, which provides emergency assistance to local authorities after flooding.

Before the visit, he said: “First of all, our hearts must go out to families who have been driven out of their homes by flood water, many of whom will have had a very worrying 48 hours stuck in their homes, and I think the emergency services have done a brilliant job. What we must do now is make sure everything is done to help in this vital phase of dealing with the floods.

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“Then there’s the vital recovery phase where we need to try and help people get their insurance claims and help people get back into their homes. We should sit down again with the Environment Agency and look at the flood schemes that have been built, look at the ones that are planned … and ask what can we do, what’s in the plan for the future and how does that need to change.”

The government will be desperate for the flooding not to become a political crisis as happened in January 2014, when ministers were accused of not doing enough to help people on the Somerset Levels. At the time of those floods, funding for defences became a prominent political issue, with the government clashing with Labour about whether there had been cuts.