European Commissioner for Competition Margrethe Vestager has signalled that she plans to investigate the European tax affairs of further US multinationals, less than three weeks on from delivering the verdict that Ireland had given Apple billions in illegal state aid.

Judging by her comments on Twitter, companies associated with the Business Roundtable group could come in for particular scrutiny.

Business Roundtable comprises 185 American CEOs, with the group writing to German Chancellor Angela Merkel last week asking her to intervene in Vestager's ruling that Apple must pay Ireland €13 billion in back taxes.

It says that its companies take a total of $7 trillion in revenues annually, while the likes of Jamie Dimon of JP Morgan Chase and Jeffrey Immelt of General Electric are listed as members.

Davide Serra, the founder of Algebris Investments, tweeted Vestager in relation to the letter:

"Apple : so in the USA there are 185 CEO which think it's legal to pay 0.05% Taxes in Europe! @vestager pls check what they pay asap!"

Vestager responded:

"I will. And I keep thinking about all the CEOs who just make sure that their companies do pay their taxes. They exist too."

In an interview published in German business newspaper Handelsblatt on Sunday, Vestager said:

"It is 100% legitimate to tax profit where it is generated.

"From our perspective, it is irritating when American companies pay less in taxes than European ones."

The European Commission is currently investigating the tax payments of McDonald's in Luxembourg, with the Financial Times reporting that the fast food giant is facing a tax bill of up to $500 million.

Its review found that the company paid an average tax rate of 1.49% on profits of $1.8bn since its Luxembourg headquarters were reorganised seven years ago. The standard tax rate in Luxembourg is 29.2%.

When the probe was launched in late 2015, Vestager said:

"A tax ruling that agrees to McDonald's paying no tax on their European royalties either in Luxembourg or in the US has to be looked at very carefully under EU state aid rules.

"The purpose of double taxation treaties between countries is to avoid double taxation – not to justify double non-taxation."

McDonald's has denied that it has received "any preferential treatment".