This warning comes just months after the Market Research Society (MRS) accused the Conservative Party of breaching data protection rules with an online survey – accusations challenged by the party as “unfounded and baseless”.

“We have received a number of queries and concerns about political parties’ use of surveys,” Information Commissioner Christopher Graham wrote in the letter. “We recognise that research is an important tool for the development of policies and our guidance makes clear that a political campaign can conduct genuine research in the same way that professional market research companies do to help inform their views and formulate policies.

“However, communications claiming to be for research that are also intended to gain support now or at some point in the future are covered by direct marketing rules.”

The ICO has also written directly to MRS chief executive Jane Frost, in response to the MRS’s accusations, to confirm that the Conservative Party’s survey had failed to follow ICO good practice guidelines. However, following subsequent changes to wording, the ICO decided to take no further action.

The ICO has produced detailed guidance on data protection and electronic marketing rules in relation to political campaigning.