A committee of British lawmakers on Wednesday said that their voter registration website could have been hacked by “foreign governments” ahead of the Brexit referendum, Reuters reported. The website had crashed on June 7, 2016, just before the deadline for people to register their vote. At that time, the government had said the website crashed because more than 500,000 people were trying to register on the final day.

The Parliament’s Public Administration and Constitutional Affairs Committee said there was no evidence to prove the allegations, but “there were indications that there was a distributed denial of service (DDoS) attack by hackers using botnets”, reported BBC. The DDoS attack slows down the system and forces it to crash or shut down. However, the committee said the alleged foreign interference may not have had any effect on the final outcome.

“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 report said.

The report also criticised then Prime Minister David Cameron for calling the referendum in the first place. “There was no proper planning for a Leave vote so the EU referendum opened up much new controversy and left the prime minister’s credibility destroyed,” the report said according to Reuters.

Cameron who had backed staying in the European Union had resigned from the post of the prime minister after the results of the referendum were out.

The report asked for the civil service code to be amended to ensure officials are “impartial” during referendum campaigns, The Telegraph reported. “The use of the machinery of Government during the referendum contributed to a perception that the civil service were, in some way, biased. That any such perception exists was deeply regrettable and entirely avoidable,” the report added.