European Union flags are seen outside the EU Commission headquarters in Brussels, Belgium April 1, 2019. REUTERS/Francois Lenoir

BRUSSELS (Reuters) - Britain will have to recover millions of euros from some multinationals after EU antitrust regulators ruled on Tuesday that an exemption in a UK tax scheme was illegal.

The European Commission’s decision, following a 16-month investigation, is part of an ongoing crackdown against multinationals benefiting from sweetheart tax deals offered by EU countries.

The EU investigation focussed on Britain’s Controlled Foreign Company (CFC) rules, which are aimed at attracting companies to set up headquarters in Britain and discourage UK companies moving offshore.

The EU competition regulator said an exemption in the scheme for interest income earned by offshore subsidiaries between 2013 and 2018 - which had been criticised by tax campaigners as a major loophole - flouted EU laws.

“The UK gave certain multinationals a selective advantage by granting them an unjustified exemption from UK anti–tax avoidance rules. This is illegal under EU State aid rules,” European Competition Commissioner Margrethe Vestager said.

The Commission said the exemption could be justified if interest payments received from loans did not result from British activities. However, if they were derived from UK activities, the exemption would not be justified.

The Commission did not say which multinationals are affected nor did it give an estimate for the amount Britain would recover, leaving it to UK tax authorities to reassess the tax liabilities.

BBA Aviation, Chemring, Daily Mail & General, Diageo, Euromoney, Inchcape, London Stock Exchange, Meggitt, Smith & Nephew and WPP are some of the companies which have mentioned the EU investigation in their accounts.

Vestager has already ordered Apple, Starbucks, Fiat Chrysler and several other multinationals to pay back taxes totalling billions of euros to various EU countries.