The chief executive of the body, Alistair Buchanan, said the findings proved that npower needed to do more to match the efforts made on the issue by other suppliers.
He explained: "At a time when some energy suppliers have announced double-digit price rises, it is vital that suppliers ensure they are offering the best support to people in debt or danger of falling into debt."
Ofgem's concerns over the high disconnection rate of npower has come after the energy provider recently increased the price of its energy tariffs for household customers.
The decision to increase its gas and electricity costs by 12.7 per cent and 17.2 per cent respectively was described as "not an easy one" by the firm's managing director Giuseppe Di Vita.
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