Dozens of towns in the states of Alagoas and Pernambuco, some of the poorest in Brazil, have been inundated and more than 1,000 people are missing following heavy rain.
The rising flood waters forced 100,000 people to flee their homes and tens of thousands are now homeless, with several towns cut off by the water.
Joao Martinez da Cruz, Tearfund's Country representative for Brazil, said reports he had received pointed to considerable damage to infrastructure:
'Roads were washed away by the rains, hindering the delivery of aid to affected areas.
'Overturned cars lay among the debris of hundreds of shattered houses and railway tracks were torn apart by the force of the water.'
Tearfund partners Diaconia, RENAS and the Salvation Army are helping survivors, with the response effort being coordinated by the Brazilian Civil Defence Agency.
Drinking water, shelter, food, blankets, medicines and bedding are among the essentials urgently needed.
The Brazilian government has promised US$56 million to the relief effort and has dispatched the country's armed forces to assist the civilian authorities.