Spending cuts could leave 240,000 extra households facing a "significant risk" of flood damage within 20 years, ministers were told.
A document presented to ministers in November last year - just days before the Cumbria was inundated - warned of the risks posed by extreme weather events becoming more frequent.
Details of the paper were reported in the Observer as parts of the UK braced for more heavy rain and David Cameron announced a £40 million package to bolster defences in areas hit by Storm Eva.
The document, drawn up by the Association of Drainage Authorities, which represents a range of organisations responsible for managing water levels, said: We have had the five wettest years since 2000. The Environment Agency's funding for maintaining flood assets has fallen by 14%. Downward adjustments have also been made to intended revenue spending commitments."
It warned that "failure of assets and networks is more likely as extreme weather events become more frequent and unpredictable" and recommended a change in approach to a more long-term strategy.
Referring to the potential impact of spending cuts, the document said: "Annual flood and storm damage costs are approximately £1.1 billion, according to the Association of British Insurers, and those households at significant risk (of flood damage) through a reduction in our capacity to manage water levels could increase from 330,000 today to 570,000 in 2035."
The document said cuts to local authority budgets had left them with little option but to reduce funding to drainage boards and other organisations and landowners who manage river levels, the Observer reported.
"Such reductions in investment mean that some river, watercourse and sea defence systems and structures are maintained only to a minimal level; consequently the useful lives of those assets will be reduced," the paper said.
"The rivers and coasts of some rural areas are at a major crossroads and their funding is purely based on the benefits of flood risk to people and property as calculated currently. The Environment Agency has ... reduced the extent of their watercourse channel maintenance and taken steps to stop operating a number of structures and systems. Examples include lowland catchments across Lancashire and Cumbria."
The Department for the Environment, Food and Rural Affairs (Defra) insisted that funding was in place for schemes to protect hundreds of thousands of homes.
A Defra spokeswoman said: "We are exceeding the Government's manifesto commitment by building 1,500 new flood defence schemes that will better protect 300,000 more homes. That's an extra £2.3 billion of capital investment to help our most at-risk communities over six years."
Mr Cameron announced that £40 million would be spent on fixing and bolstering flood defences battered by Storm Eva.
Charities raising cash for communities left devastated over Christmas by the deluge will be matched by the Government up to a total of £2 million in a move echoing pledges to earlier flooding victims.
Thousands of homes and businesses across large swathes of northern England were hit by severe flooding as the storm wreaked havoc on Boxing Day.
Mr Cameron said: "I have seen at first-hand the devastation caused by flooding. And that's why this work to repair and improve flood defences is so vital."
Around £10 million of the funding package will be used to improve defences in York after they failed to cope during the storm. Environment Agency officials decided to lift the Foss Barrier designed to protect the city after finding its pumps were at risk of electrical failure due to water entering the building, prompting widespread anger among residents.
The rest of the cash will be spent on repairing defences on the Calder, Aire, Ouse and Derwent rivers in Yorkshire as well as the Wharfe, which runs through Tadcaster where the storm left the town split in two when an ancient bridge collapsed.
Mr Cameron has also made Transport Minister Robert Goodwill a "flooding envoy" for Yorkshire to oversee the response in the region and identify what must be done to protect the area in the future.
More heavy rain is set to lash parts of Britain over the coming days, with some areas of eastern Scotland likely to see more than 200mm between Saturday and Monday.
Met Office chief meteorologist Frank Saunders said: "We expect heavy and persistent rain to affect parts of eastern Scotland over the next few days, and have already issued national severe weather warnings for its potential impacts.
"Everyone should be aware of the potential for disruption in places from further flooding especially in areas such as Perth and Kinross, Angus and Aberdeenshire, where amber 'be prepared' warnings are in place."
Vincent Fitzsimons, the Scottish Environment Protection Agency (SEPA) hydrology duty manager, said: "Flood impacts may affect communities and cause disruption to travel and infrastructure from Tayside to Angus to Aberdeenshire over the coming days.
"Localised flooding is also possible in parts of the Scottish Borders, and in Caithness and Sutherland during Sunday and Monday."
The Environment Agency said more rain is expected on Sunday in south-west and north-east England and this will bring a risk of flooding along parts of some rivers in Devon and Cornwall and the North East.
It said the River Ouse is set to remain high in York for several days and the River Severn will remain high in places, bringing a low risk of flooding over the weekend and into next week in Shropshire, Telford and Wrekin, Worcestershire and Gloucestershire.
Temporary defences have been deployed in Shrewsbury and Bewdley.