A 100-mile stretch of the River Severn was described by the Environment Agency as "critical", and Herefordshire was declared a "major incident area" after flooded roads cut off villages in the north-west of the county.
Flood warnings were also issued in parts of Wales, where the emergency services were considering the evacuation of people from their homes.
The Environment Agency, which has been heavily criticised for its response to the Easter floods this year, said that it was redeploying staff to the most vulnerable areas and warning people living near rivers to stay alert.
Bryan Utteridge, the agency's head of flood defence, said yesterday: "We are extremely concerned about the situation on the River Severn. The high flows on the river have been caused by heavy rain which fell on the Welsh hills at the weekend finding its way to the sea. This already difficult situation has been exacerbated by the recent heavy rain falling directly on the River Severn area."
The renewed flood warnings came after a weekend of torrential weather which is believed to have claimed up to 12 lives.
A spokesman for West Mercia Police said: "The water level is expected to be one to two feet higher than weekend levels. North-west Herefordshire is the worst affected area, where some villages have been cut off.
"Whereas the River Wye was the principal offender over the weekend, the Lugg and the Arrow are now adding to the problems. We may have to evacuate people."
Evacuations also seemed likely in Wales last night. Flood warnings were issued in areas near the Wye, Lugg, Monnow and Usk rivers.
A spokesman for the Environment Agency said: "We understand that they [the emergency services] are currently considering evacuation of properties in villages such as Melverley, Pentre and Llandrinio, near to where the rivers Severn and Vyrnwy meet."
A spokesman for the Met Office said that the wet weather was set to continue until the weekend, when there would also be the possibility of gales.
The Environment Agency said that Shrewsbury, which has been on red flood alert for five days, could experience its worst flooding for 50 years this morning.
"All the riverside towns along the Severn from Welshpool to Worcester are severely affected by flooding," a spokesman said.
The rivers Vyrnwy, Wye, Lugg and Upper Severn are also expected to remain at the most serious level of alert for the rest of today, he added.
The Environment Agency said flood warnings were being issued directly to people living in vulnerable areas using automatic telephone dialling systems. People were also warned to listen to their local radio stations.
Martin Airey, senior forecaster at the PA WeatherCentre, warned that more heavy rain was expected across England and Wales by the end of the week.
"In terms of causing floods, it should be a bit drier over the next couple of days but Saturday and Sunday could see a repeat performance of last weekend.
"The weather for the next two days will be around 10C but it will seem colder because of the wind," he said.Reuse content