Oliver Letwin broke the law when he dumped confidential documents in public bins, the Information Commissioner (ICO) has said.
In October the Cabinet Office minister had to apolgise after the Daily Mirror photographed him repeatedly dropping documents in St James Park bins.
On Tuesday the Information Commissioner Christopher Graham said the West Dorset MP’s disposal of constituency paperwork in public bins constituted a breach of the Data Protection Act.
Graham said Letwin has signed a written commitment to put changes in place, including ensuring that any documents containing personal data are disposed of in a secure manner.
He said that David Cameron's policy guru had "learned" from his mistake and was lucky that none of the papers contained particularly sensitive data.
“Constituents entrust their Member of Parliament with all sorts of personal information and should never expect the details of the concerns they’ve raised in confidence to end up in a park bin for anyone to see," he said.
"It is clear that Mr Letwin has learned from this incident and we’re pleased that he has co-operated fully.
“It is fortunate that most of the information he discarded was not of a particularly sensitive nature and was therefore unlikely to cause substantial distress to his constituents.
"But if we receive any further reports or complaints about Mr Letwin’s conduct in this area then we will consider taking more formal action. I’m sure this case will also prompt other MPs to review their handling of personal data to ensure they’re doing all they can to keep it secure."
Graham launched an investigation into Letwin's actions after the Daily Mirror made a complaint against him.
The ICO found that the letters and emails contained the names, addresses and contact details of approximately 20 people.
One email also included a limited amount of information relating to an individual’s recent hospital treatment.