Facebook has told the parliamentary fake news inquiry it will expand its investigation into whether Russian agents attempted to influence the Brexit vote.

In a letter to Damian Collins, chair of the Digital, Culture, Media and Sport (DCMS) Committee, Facebook’s head of policy in the UK, Simon Milner, said the social media giant would now search for “clusters engaged in coordinated activity around the Brexit referendum” which appear to have originated in Russia.

“It is right that companies like Facebook should initiate their own research into issues like this where there is such clear public concern, and not just act on intelligence that has been passed to them,” Mr Collins, who leads the committee’s fake news inquiry, said in a statement. “They are best placed to investigate activity on their platform.”

Facebook said security experts would begin their investigation “promptly” but may take several weeks to produce results.

Mr Collins had previously slammed Facebook for doing “no work” in looking for Russian interference on their platform during the 2016 referendum, after the company submitted evidence to the Electoral Commission in December of accounts which were active during the US Election.

In the letter, Mr Milner said Facebook believed those accounts, identified as part of Russia’s “Internet Research Agency” of trolls and propagandists, “seemed to be the most likely area” to find evidence of meddling in the UK but added that the company would now look deeper into its records.

“I look forward to seeing the results of this investigation, and I’m sure we will want to question Facebook about this when we know the outcome,” said Mr Collins.

Executives from Facebook, Twitter and Google are due to give evidence to the parliamentary inquiry into fake news in February, when MPs visit Washington for the occasion.