The Labour Party has been served an enforcement notice by the Information Commissioner’s Office for making unsolicited automated marketing calls.
According to the ICO’s notice, the Labour Party has breached the Privacy and Electronic Communications Regulations by making calls to promote the party to around 495,000 people, without their consent.
The notice requires Labour to cease making such calls, and failure to comply is a criminal offence and could lead to prosecution.
A Labour Party spokesperson said: "The Labour Party considered advice from the Information Commissioner’s Office prior to making these calls and believed that we had abided by this advice. We will now examine this decision in detail."
The party has 28 days from the enforcement notice date (4 February) to appeal the decision. It should also cease making the calls within 30 days of the notice.
ICO investigated a complaint in July 2007 from an individual who had complained that he had received an automated marketing telephone call from the Labour Party despite never consenting to receive such calls.
The call consisted of a recorded message from former Coronation Street actress Liz Dawn.
After seeing a transcript of the message, the ICO advised the Labour Party that the content constituted direct marketing. The party agreed to stop making calls using the script or anything similar.
However, in June 2009, the ICO received further complaints from The Scottish National Party and a member of the public.
They reported that unsolicited automated calls consisting of the same message had been made encouraging recipients to vote in the local and European elections.
Labour confirmed that the calls were made to people in apparently Labour supporting areas, and that most of the numbers were obtained using commercially purchased lists.
David Smith, deputy commissioner at the ICO, said: "The ICO has consistently made clear that the promotion of a political party counts as marketing.
"The Labour Party has breached privacy rules by making automated marketing calls to individuals who have not consented to receiving such calls.
"The fact that the calls were targeted at what were believed to be Labour supporting areas confirmed our view that they were designed to promote the Labour Party’s electoral cause by encouraging Labour supporters to vote."
The ICO has served enforcement notices to other political parties before for the same type of regulation breach. The Conservative Party and the Scottish National Party both received notices in October 2005, while the Liberal Democrats received a notice in 2008.
This was despite the ICO having written to all the major political parties in April 2005 to remind them of the updated guidance and regulations.