Penny Pritzker, the US secretary of commerce said in an interview, "The folks in Brussels would tell us that it is a coincidence," when facing a question about the number of US firms who are being pursued under EU regulations.

When asked if she believed that, she replied, "I take them at face value."

At the moment Apple and Amazon are being investigated for sweetheart tax deals (with the former involving the Californian group's operations in Ireland) - Facebook has also been plagued with criticisms of its privacy policies, while Google has been wrapped up in an antitrust investigation.

The EU has pledged to create a “digital single market” (DSM) applying the Union's free trade ideas to 21st century industries.

Ms Pritzker spent two days in Brussels last week - US interests fear the at the reimagining of EU's digital economy could create new regulations which will make it harder for US firms to operate in Europe.

The White House's decision to send the secretary to Europe has been read as a sign that there is unease in Washington at how new rules could affect US firms.

'Safe harbour' laws are a potential flash-point - they allow US companies to transfer data from Europe back to the US without breaking EU rules.

This issue is complicated by Edward Snowden's claims, and leaked NSA documents from the US, which suggest that the same protection has not been afforded to European firms in the US.

In Brussels Ms Pritzker suggested the potential for a rift between the US and the EU has been overstated, saying:

“The rhetoric before the DSM came out was very different to the tone of the document itself.”

She conceded that both sides have different attitudes towards how data should be treated, but added that there is also "a lot of overlap."