The Family Welfare Association has taken over the services of another family support charity, the Family Service Unit, after the latter was forced into administration.
The FSU invited the FWA and other interested parties to bid for its services after it ran up debts that are believed to amount to £4m.
"The FSU has ended up owing huge sums of money because it bought into a local authority pension scheme that was in deficit," said Helen Dent, chief executive of the FWA. "It was looking for someone to take it over."
The FWA beat off three other bidders to take over the services earlier this month. It does not, however, take on the FSU's debts.
"We've taken over the services, but we haven't taken over the whole organisation," said Dent. The debts remain with the FSU's head office, which has now gone into administration. The takeover turns the FWA into the largest family support organisation in England.
Dent said the number of redundancies among service staff was "minimal".