The prime minister is expected to chair a Cobra emergency committee meeting later in response to flooding in northern England.
The Environment Agency has 39 flood alerts, including five severe on the Don River in South Yorkshire.
About 400 houses were flooded and 1,200 properties were evacuated.
Prior to the government announcement, Labor leader Jeremy Corbyn had invited Boris Johnson to summon Cobra.
Corbyn asked the prime minister to "take charge" of the situation himself and said he disagreed with Johnson's assessment over the weekend that the floods were not "a national emergency."
He wrote to Johnson, saying: "If this had happened in Surrey, not in Yorkshire or the East Midlands, it seems much more likely that a national emergency would have been declared."
A government spokesman said: "The prime minister will chair an emergency meeting … [Tuesday] to discuss the response to recent floods. "
A yellow rain warning remains in some parts of Yorkshire and the East Midlands for Monday, Tuesday and Thursday, and an emergency appeal to support "displaced" families has raised nearly £ 50,000.
The Doncaster Council asked people to evacuate the village of Fishlake, saying "it can only offer dedicated support to people who are not in a life-threatening area."
But farmers say they can't leave because they have to take care of their animals.
Joe Howslam, 23, told the BBC: "I live in Fishlake with my parents, brother and sister, but we all had to move.
"In Fishlake's history it has never been so bad, according to some of the older members of our village.
"I'm a heavy truck mechanic and we run a family farm, so I borrowed a tractor on Saturday and helped rescue some people. I even saved my father from the upper window of the house."
"There is about a meter of water downstairs, so the washer, dishwasher, etc. are all under water and ruined. We managed to get some things out of the room, but not all of them."
He said he heard reports of looting in the village, but added that family members regularly return to the area.
- Community rallies to help flood-hit residents
Four Environmental Agency bombs are in Fishlake to remove floodwaters from the village.
The local church is collecting food to hand out to residents and baked dinners were delivered on Sunday to those who stayed at their homes.
Empty caskets were seen floating inside the workshop of a flooded funeral home in the village.
Tractors and boats were used to navigate the village, with many roads in the area under flood water.
According to the Salvation Army, some people have been rescued from their boat houses since the early hours of Saturday, but others remain on their properties as military helicopters. was used to help increase flood defenses in the area.
Twelve flood alerts remain in Lincolnshire, where more than 1,000 acres were flooded by Barlings Eau and some farms were cleared, with some railway lines still blocked by high tide.
Northern said your services in Rotherham Central they were not working until further notice, with reduced service between Doncaster and Sheffield. CrossCountry trains are being diverted away from Doncaster.
Doncaster Council said several roads remain closed.
The RSPCA has been involved in a rescue operation to save 60 swans following a flooding oil spill on Rotherham.
Further south, parts of Derbyshire are still affected by the floods.
Areas around Matlock – where former Derbyshire sheriff Annie Hall was swept to death by the flooded Derwent River – continue their cleanup efforts, with more weekend rains leaving standing water along several roads.
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