The data broking company, which provides advice on pregnancy and childcare, sold the information to Experian Marketing Services, a branch of the credit reference agency, specifically for use by the Labour Party. Experian then created a database which the party used to profile the new mums in the run up to the 2017 General Election.

The Labour Party was then able to send targeted direct mail to mums living in areas with marginal seats about its intention to protect Sure Start Children’s centres.

The ICO investigation found that Emma’s Diary’s privacy policy did not disclose that the personal information given would be used for political marketing or by political parties. This is a breach of the Data Protection Act 1998.

Elizabeth Denham, information commissioner said: “The relationship between data brokers, political parties and campaigns is complex. Even though this company was not directly involved in political campaigning, the democratic process must be transparent.”

This case formed part of the ICO’s comprehensive investigation into data analytics for political purposes. The ICO announced its intention to fine Emma’s Diary when it published its interim investigation report on 11 July. Representations from the company have been considered and today’s announcement confirms the monetary penalty.

The partner policy report, Democracy Disrupted? Personal information and political influence, sets out how the ICO aims to stop personal data being used incorrectly in campaigns during future elections.

Ms Denham continued: “All organisations involved in political campaigning must use personal information in ways that are transparent, lawful and understood by the UK public.”

The ICO has put the UK’s 11 main political parties on notice to have their data-sharing practices audited later this year. The ICO also has outstanding enquiries with a number of data brokers, including Experian.

Ms Denham added: “The ICO is committed to monitoring data brokers, political parties and online platforms and using new audit and enforcement powers so that the public can have confidence that parties and political campaign groups are complying with the law.”