The chairman of the Environment Agency has hit back at ministers in a growing row over the handling of devastating winter storms.
As thousands of families along the River Thames braced for more flooding, Lord Smith insisted his staff knew "a hundred times" more than any politician.
He also squarely blamed Treasury funding rules for failure to dredge rivers, and again insisted he had no intention of resigning.
The intervention, in an interview with BBC Radio 4's Today programme, came after Communities Secretary Eric Pickles issued a barbed apology for taking Environment Agency (EA) advice - saying ministers had "thought we were dealing with experts".
Lord Smith said he had "kept his counsel" up until now over Government funding and rules.
"When I hear someone criticising the expertise and professionalism of my staff in the Environment Agency who know more about flood risk management - 100 times more about flood risk management - than any politician ever does, I am not, I'm afraid, going to sit idly by," he said.
"The EA is bound by the rules that are laid down by the Government. So when someone says that we followed the advice of the EA, what they were actually doing is following the Treasury rules that say how much we can spend and how much we cannot spend on any individual flood defence scheme."
The former Labour Cabinet minister said the EA was previously permitted to allocate only £400,000 to Somerset, and no other funding came forward.
"The situation now has completely changed because not only has the Government come up with some extra money for Somerset, but they have said the Treasury rules won't apply to Somerset."
He added that "money absolutely is a big part of the issue".
Lord Smith was asked about reports that Environment Secretary Owen Paterson, who was leading the Government flooding response before being forced to undergo an eye operation, complained to Downing Street about Mr Pickles' criticism of the EA.
"I have indeed spoken with Owen Paterson by text... he has been hugely supportive throughout of the Environment Agency, its staff and its work and I very much appreciate that."