MPs have released a report which suggests foreign hackers might have brought down a key EU referendum website on the eve of last summer's vote - and suggested Russia and China are potential suspects.
The voting registration website crashed on June 7, shortly before the deadline. At the time, the crash was attributed to a surge of interest in the wake of TV debates and campaigning.
But now MPs from the Public Administration Committee have released a report which says a foreign cyber attack can't be ruled out.
It claims the crash had "indications" of a Distributed Denial of Service attack (D-DOS) - a type of cyber attack where a network is flooded with traffic and requests, in an attempt to disrupt normal functions - but did not give evidence for this possibility.
Hacking has been high on the news agenda for months, with Russian hackers accused of influencing last year's US presidential election.
The report doesn't accuse Russia directly, but it does say "Russia and China use a cognitive approach [to hacking] based on understanding of mass psychology and of how to exploit individuals.
"The implications of this different understanding of cyber-attack, as purely technical or as reaching beyond the digital to influence public opinion, for the interference in elections and referendums are clear."
The Cabinet Office disputed suggestions of hacking in an interview with the BBC, reiterating that the crash was caused by a spike in users and didn't appear to be as a result of "malign intervention".