The Observer has obtained a series of Conservative party attack ads sent to voters last week in the key marginal constituency of Delyn, north Wales. Activists captured the ads using dummy Facebook accounts after finding that their own ad - encouraging young people to register to vote - were being "drowned out" by the Tory ads.

The Conservatives have refused to supply examples of adverts the party is sending to individual voters on Facebook, despite growing concern over unregulated online election activity.

Following a series of articles in the Observer concerning the use of data by Vote Leave and Leave.EU during last year's referendum, the Information Commissioner's Office has launched a wide-ranging investigation over possible breaches of UK data laws.