An independent inquiry set up after the floods has found serious flaws in the way in which the Environment Agency dealt with the disaster in central and eastern England and mid-Wales.
But Peter Bye, the inquiry chairman, also blamed a more fundamental problem - that some local authorities have repeatedly rejected official advice not to build on flood plains.
Announcing his interim findings, Mr Bye said the Environment Agency had a "sturdy framework" of policies and plans to deal with flood warning and defence. But faced with floods as bad as this century's benchmark disaster of 1947, the agency failed to give proper warnings and there was a breakdown of co-operation with other bodies.
"There is evidence in some locations of unsatisfactory forecasting and warning dissemination, apparent slow reaction to events, confusion and misunderstanding amongst the public ... and unsatisfactory liaison between agency staff and emergency services," the report concluded.
It found that some of the agency's maps were "inadequate" for describing flood-risk areas and it appeared that fax messages were sent to the wrong numbers during the emergency.
"Greater emphasis should be given in the future to testing response activity, interfacing and co-operation, with extreme event scenarios," the report said. But Mr Bye, the former chief executive of Suffolk County Council, said blame had to be shared by local authorities which had allowed development on flood plains, against clear advice from the agency and its predecessor bodies.
Nearly all the caravan sites affected by the flooding were opposed at the planning stage - for example, a new leisure centre at Banbury, which was badly hit.
The agency estimated that 10-15 per cent of local authorities approved developments against its advice. Dr Geoff Mance, its water management director, said the problem must be taken more seriously: "With 4.5 million new homes coming, we need to look for more national innovative thinking in design. We shouldn't always be thinking about flood defences.
The use of materials such as Tarmac and concrete increases the rapid run-off of water into rivers, creating problems more quickly than in the past. At Easter, 75mm of rain fell in 36 hours in some areas, the equivalent to six weeks' average rainfall.
Archie Robertson, the Environment Agency's director of operations, said he wanted to reassure the public that the agency was treating the matter seriously. It would reassess the trigger points for flood warnings and planned early meetings with emergency services, he said. But he added that the work would cost money and the agency was already underfunded by an estimated pounds 30-pounds 40m a year.
Mr Bye said that detailed investigations would be conducted in areas which were particularly badly hit.Reuse content