Wonga has escaped criminal investigation into allegations that the payday lender sent letters to customers falsely claiming to be from lawyers.
The City of London police confirmed today that it would not take the matter any further, saying there was not sufficient evidence to pursue the matter.
The case was reopened by the police last summer, having initially decided it was a matter for the Financial Conduct Authority.
Customers received letters from made-up companies using fictitious names such as Barker and Lowe Legal Recoveries, and Chainey, D’Amato and Shannon from October 2008 to November 2010.
Wonga, which bills itself as a “straight-talking” lender, has already been slapped with a £2.6m bill for customer compensation as a result of the FCA's investigation.
The letters were used to keep "piling the pressure on customers", an investigation by the watchdog concluded.
At the time, interim chief executive Tim Weller - who was not in charge during the period in question - issued an unreserved apology to "anyone affected by the historical debt collection activity and for any distress caused as a result".
The firm said no staff directly involved were still at the lender.