The newspaper's parent company was in breach of direct marketing rules according to the ICO.
Telegraph Media Group has been fined £30,000 by the Information Commissioner's Office (ICO) over an election day email, which was delivered to hundreds of thousands of readers, urging them to vote Conservative.
Penned by editor Chris Evans, the letter was sent out subscribers of the paper's newsletter. It called the 2015 general election the “most important since 1979” and stated: "The Daily Telegraph urges its readers to vote conservative."
The ICO said that recipients had not give specific consent to receive this type of marketing and as such deemed the broadsheet to have broken Privacy and Electronic Communications Regulations (PECR).
The campaign letter was described as "negligent" by the ICO's head of enforcement, Steve Eckersley.
“People may well perceive the paper’s editorial content to have a political bias, but when the Telegraph emailed people directly, calling for them to vote for a political party, they crossed a line," he said.
Earlier this year the Independent Press Standards Organisation (Ipso) said that the a piece printed by the Telegraph in the lead up to the general election under the headline 'Sturgeon’s secret backing for Cameron' had breached the editor's code on practice.
The front page article reportedly contained the contents of a leaked government memo which claimed that Scottish first minister Nicola Sturgeon, had said she would rather see David Cameron win the general election over Ed Miliband.
The media watchdog dubbed the story “misleading".