LONDON (AP) — British lawmakers investigating the use of Facebook users’ information in political campaigns issued a summons Thursday for the former head of data firm Cambridge Analytica after he declined to answer their questions.

Parliament’s Digital, Culture, Media and Sport Committee said it had summoned the company’s ex-chief executive, Alexander Nix, to appear June 6.

It also issued a summons for Dominic Cummings, former director of the Vote Leave campaign in Britain’s 2016 European Union membership referendum. It wants him to answer questions May 22.

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Last month Nix refused to appear before the committee, citing British authorities’ ongoing investigation into Cambridge Analytica.

Committee chairman Damian Collins said Nix and Cummings could be found in contempt of Parliament if they ignored the summons.

Former Cambridge Analytica staffer Christopher Wylie sparked a global debate over electronic privacy when he alleged the company used data from tens of millions of Facebook accounts to help U.S. President Donald Trump’s 2016 election campaign. Wylie said the Brexit “leave” campaign also had access to the Facebook data.

Cambridge Analytica announced last week that it plans to file for bankruptcy in Britain and the United States, saying negative publicity from the scandal had driven potential clients away.

The House of Commons can punish people “for disorderly and disrespectful acts committed against it” although in practice its powers are limited.

In the past offenders could be imprisoned in a special cell in Parliament, but the power has not been used since 1880. Parliament also once had the power to fine those found in contempt, but it has not done so since the 17th century.