Flooded homes along the River Thames are being evacuated and thousands more are at risk, with water levels expected to rise further over the next 24 hours.
Residents in one Berkshire village say the scenes are from a "horror movie".
Fourteen severe flood warnings are in place in Berkshire and Surrey, while two remain in Somerset.
PM David Cameron - who is in flood-hit Dorset - said it was not the time to change personnel amid criticism of Environment Agency head Lord Smith.
Communities Secretary Eric Pickles has been answering an urgent question put by Labour in the Commons on the flooding crisis.
Homes in the Berkshire village of Datchet are underwater and hundreds more along the lower River Thames, as far as Shepperton, are under threat, the Environment Agency says.
Several Thames gauges are showing their highest levels since being installed in the 1980s and 90s.
Fire crews, who have been rescuing people from their homes in Staines, say they have never known waters so deep or a flood rescue operation on this scale.
In Windsor, Councillor Colin Rayner pleaded for the police and Army for help.
"We've got 50 volunteers here, we've got the vulnerable people out of their homes, now we need to get everyone else out," he said
Nearby, in the Berkshire village of Colnbrook, resident Asif Khan said his whole street was under water, his house was flooded and his fridge "just went bang".
"It's something out of a horror movie," he said, adding that he was now about to try to evacuate with his two small children.
Hurst village resident Paul Palmer said sewers there were blocked and they have been unable to use the toilet since Friday.
"It's starting to back up into the toilet - it's like going back to the dark ages," he told the BBC.
The urgent Commons question from Labour follows a deepening political row.
Mr Pickles, who is standing in for Environment Secretary Owen Paterson, told MPs that there was a "high risk that the Thames, the Severn and the Wye will flood in the middle of the week".
But he said extra efforts were being made to deal with the problem.
"It is wrong to suggest that I have issued even the slightest criticism of the work of the Environment Agency. I believe we should work together, and not to make silly party political points," he added. Last week, Mr Pickles said ministers had been given bad advice by the agency over river dredging.
Agency chairman Lord Smith hit back, saying his staff knew "100 times" more about flooding than any politician and insisted again he would not resign.
Speaking from Portland, off the Dorset coast, Mr Cameron said: "I am only interested in one thing and that is making sure that everything government can do is being done and will go on being done to help people through this difficult time.