Ministers are failing to protect the UK's most valuable farmland from flooding, posing a long-term risk to the security of UK food production, according to an influential group of MPs.

A run of poor weather since 2011 has led to extensive flooding of properties but has also severely dented the production of many foods, with the UK now being a net importer of wheat.

The environment select committee's report also said the government's spending by the Department for Environment, Food and Rural Affairs (Defra) to protect homes from flooding is not keeping pace with the rising risk, which is increasing as climate change intensifies downpours, and were also failing to act effectively to block the building of new homes on floodplains.

"Record rainfall in the past two years has led to extensive flooding, cost the economy millions and caused disruption and distress to householders and communities across the UK," said Anne McIntosh, a Conservative MP, and chair of the commons select committee on environment, food and rural affairs.

"Additional capital funding for flood defences [announced last Thursday] is welcome since every £1 spent on flood defences to protect communities spurs growth and delivers economic benefits worth £8."

The report found that the current model for deciding which flood defences to build is biased towards protecting property. "This means funding is largely allocated to urban areas. Defra's failure to protect rural areas poses a long term risk to the security of UK food production as a high proportion of the most valuable agricultural land is at risk of flooding," the MPs reported.

Flood defence spending crashed by over 25% year-on-year after the coalition came to power, despite the government's scientists showing that global warming was driving up flood risk. One in five homes in England and Wales is at risk of river or coastal flooding, with more also threatened by flash flooding, according to the Environment Agency.

Ministers announced on last Thursday that funding would jump to record levels of £370m a year from 2015-16 and then rise with inflation until the end of the decade, in part to boost economic growth and help seal a provisional deal with the insurance industry to keep premiums for homeowners in high-risk areas affordable.

But the MPs concluded: "Funding has not kept pace in recent years with an increased risk of flooding from more frequent severe weather events, and the relatively modest additional sums to be provided up to 2020 will not be sufficient to plug the funding gap."

McIntosh said: "The chancellor must ensure that investment increases by £20m year on year. We need that money over the next 25 years to protect homes and businesses better." In July 2012, the Guardian revealed that nearly 300 flood defence schemes that had been in line for funding remained unbuilt due to government cuts.

A Defra spokeswoman noted the increased funding and insurance deal and said: "Flooding is terrible for those affected, which is why we're working on long-term projects to protect people from its impacts."

The report, published on Wednesday, criticised ministers over planning policy. "We are disappointed that the coalition agreement's commitment to end unnecessary building in floodplains has not yet been translated into effective action," wrote the MPs. "Planning guidance allows building to take place too readily in areas at high flood risk."

Spending on the maintenance of flood defences and watercourses is at its lowest for many years, the MPs said, meaning cuts to those budgets were "short-sighted" and threatened to undermine the benefits gained from building new flood defences.

Ministers have pointed to a new partnership scheme, through which the private sector can contribute to new flood defences, but the report said the government had failing to secure "significant" funding in this way.

Mary Creagh, the shadow environment secretary, said: "Flooding is the biggest threat the UK faces from climate change, yet the government will spend less on flood defences in 2014/15 than Labour did in 2010. Ministers are creating uncertainty and stress for people in flood-prone areas."