BlackBerry has defended security of its smartphones, following claims that the UK Government Communications Headquarters (GCHQ) had repeatedly hacked into devices of foreign diplomats at the G20 meetings in 2009 to examine phone calls and e-mail traffic.

BlackBerry said in a statement that the firm remains confident of the superiority of BlackBerry’s mobile security platform for customers using its integrated device and enterprise server technology.

"There is no ‘back door’ pipeline to that platform," the company said.

Guardian newspaper cited a document, which reveals that delegates’ computers were monitored and phone calls were intercepted by GCHQ on the orders of the British Government.

Reports suggested that British agents also set up internet cafes mainly to enable delegates to read their email messages.

The documents reportedly suggested the operation was approved at a senior level in the government of then Prime Minister Gordon Brown.

Russia, Turkey and South Africa were among reputed targets of the GCHQ spies and they have all demanded an investigation into the report.

Further, details of the surveillance are reported to be enclosed in documents acquired by former US National Security Agency (NSA) contractor Edward Snowden, who is responsible for a string of leaks about American intelligence operations.

However, the UK has denied claims that GCHQ breached the law over US Internet monitoring programme, Prism.