The seat became vacant when the Labour Member of Parliament William Kelly resigned his seat in Parliament by accepting the post of Steward of the Manor of Northstead, a notional 'office of profit under the crown'.
[1] Kelly had been Rochdale's MP since winning the seat from the Conservatives at the 1935 general election.
[2] The Labour Party candidate was Dr Hyacinth Morgan, a doctor born in the West Indies to Irish parents, who had studied medicine in Glasgow.
[3] Although many later by-elections were contested by independent or minor party candidates, none were nominated in Rochdale.
[4] Morgan represented the constituency until the 1950 general election, when he moved to the safer seat of Warrington.