Facebook has bowed to pressure from MPs and said it will deepen its investigation into whether Russian agents used the platform to spread fake news in the hope of influencing the Brexit vote.

The social media giant told the digital, culture, media and sport committee that it would examine whether there were further clusters of accounts spreading disinformation, having previously been criticised for only conducting a limited investigation.

Simon Milner, a policy director at Facebook, said the company would carry out the work promptly to see if “there was coordinated activity similar to that which was found in the US,” where the presidential election was targeted.

Facebook had previously conducted an investigation at the behest of the UK Electoral Commission on a cluster of accounts from Russia’s “troll farm” Internet Research Agency, which were known to have spread fake news in the US.

The company concluded last month that the impact of these in Britain was limited – because the accounts spent only $0.97 (70p) for a handful of adverts before the referendum, which appeared in 200 News Feeds.

But the select committee was concerned that accounts set up to target the US presidential election may have also been aimed at the UK. It demanded that Facebook widen the scope of the investigation.

Q&A Can the Electoral Commission inquiry undermine Brexit? Show Campaigners on either side of the EU debate will have differing opinions on whether any adverse finding on spending calls the result of the referendum into question. However, Jo Maugham, the barrister behind the Good Law Project, said any illegal spending would undermine the result, adding to concerns about Russian meddling and Brexiters failing to deliver promises they made during the campaign. The commission can impose a fine of up to £20,000 for individual rule breaches. Any evidence of more serious offences uncovered in the course of the investigation can be referred to the police if warranted.

Damian Collins, the committee chair, said: “It is right that companies like Facebook should initiate their own research into issues like this,” and added that he expected that the committee would want to question the company once the inquiry concludes.

Ahead of the election of Donald Trump, the Russian Internet Research Agency spent about $100,000 on 3,000 adverts. Content from the platform was seen by up to 150m people on Facebook posts and via Instagram.

The committee is inquiring into fake news, and will travel to the US next month to meet technology executives and others to try to see what impact so called bot accounts have had.

A Guardian investigation showed that more than 400 fake Twitter accounts run by the Russian agency have tried to influence British politics recently. One fake poster attempted to stir anti-Muslim sentiment by highlighting a picture of woman it claimed was walking by a severely injured man during the Westminster terror attack.

The tweet was picked up by a number of news organisations, including Mail Online and the Sun.

But it has proved harder to obtain equivalent information about Facebook without the cooperation of the company.