Before 1945 the Dagenham area was part of the Romford constituency. The MP for the latter seat since 1935, Labour's John Parker, continued to represent Dagenham until 1983. Parker was the last serving MP to have been elected before the Second World War, and with 48 years in Parliament, remains the longest-serving Labour MP in history. The seat was first contested in the 2010 general election which resulted from the Boundary Commission's report that recommended merging the majority of the former constituencies of Dagenham and Hornchurch and added to existing electoral wards a small part of River ward was also transferred from Barking.
In 2010 Labour's Jon Cruddas took the seat despite a strong Lab–Con swing. BNP candidate Michael Barnbrook came third with 11.2% of the vote, his party's second-best showing in the 2010 election.
The constituency may retain significant pockets of poverty indicated by a high ranking in the Index of Multiple Deprivation compiled in the year 2000 however average incomes were in four large wards close to the national average. The London Borough of Barking and Dagenham saw the most rapid decrease in people of White British ethnicity in the 10 years to the 2011 census, of 31.4 percentage points. However the same dataset shows that 58.3% of people are white in the seat, which is similar to the Greater London average. An established area of settlement for British people of Asian ethnicity with 15.9% of this background, the neighbouring London Borough of Newham has a much higher proportion of residents with Asian heritage, 43.5%.
Workless claimants, registered jobseekers, were in November 2012 higher than the national average of 3.8%, at 5.5% of the population based on a statistical compilation by The Guardian.
^"Forest Heath (East of England) was the only local authority to see an increase in White British between 2001 and 2011 (by 0.8 percentage points). The proportion of White British decreased in the remaining local authorities in England and Wales, with the largest decrease in Barking and Dagenham at 31.4 percentage points." 2011 Census statistics