The Child Exploitation and Online Protection Centre (CEOP) and its parent organisation the Serious Organised Crime Agency (SOCA), have made a commitment to improving the security of its websites.
Earlier this year, the Information Commisioner's Office launched an investigation into how a reporting form on CEOP's website was found insecure by a member of the public.
A webpage used to report alleged offenders was unencrypted, with users accessing the form through a third-party website, such as Google or Facebook, reached an http address instead of the secure https URL.
CEOP, which was set up in 2006 to protect children from paedophiles online, said the issue was fixed the same day it was reported.
The ICO found that the fault had not been identified either during initial testing of the new website, or in the following months. "Several" other website security weaknesses were also revealed during the investigation.
Instead of encrypting the data before it was sent to CEOP's servers, the form was encrypted when it was received by the servers that host the website.
However, it was concluded that no data had been intercepted or compromised.
Sally Anne Poole, acting head of enforcement at the ICO, said: "Organisations must make sure that any personal data transmitted electronically is adequately protected.
"While there is no evidence to suggest that attempts have been made to access any of the information, it is highly likely that it would have been sensitive in nature and should not have been compromised by insufficient IT security measures."
CEOP and SOCA have now signed an undertaking to ensure that regular checks are carried out on its websites, and to make sure that any potential weaknesses are immediately identified.
The organisations will also make sure that any third-party website contractors are fully aware of their responsibilities in ensuring that personal data is held and transmitted securely.