Reuters reported that NSA spokeswoman Judith Emmel rejected any suggestion the US agency used the UK to do things the NSA cannot do legally.
"Any allegation that NSA relies on its foreign partners to circumvent U.S. law is absolutely false. NSA does not ask its foreign partners to undertake any intelligence activity that the U.S. government would be legally prohibited from undertaking itself," Emmel told Reuters.
Earlier this month, UK foreign secretary William Hague denied claims that GCHQ violated the law over US Internet monitoring programme, Prism.
The UK intelligence agencies are reported to have made 1,268 requests seeking information on private communications via Microsoft products including Skype in 2012.