German intelligence systematically spied on the White House and US government departments over a number of years, it has been claimed.

The damaging allegations could prove highly embarrassing for Angela Merkel and expose her to charges of hypocrisy.

The German chancellor demanded an explanation when it emerged in 2013 that the US had spied on her mobile phone, and famously said: “Spying among friends is not on”.

But according to new allegations published by Spiegel magazine on Thursday, Germany’s BND intelligence service carried out electronic surveillance on the US government over a period of eight years from 1998 to 2006.

Targets included telephones, faxes and computers in the White House, the State Department and the US Treasury Department.