with ZTE in 2011, and has also distributed modems manufactured by the Chinese firm.

"ZTE is just one of many research partners with which BT is engaged," a spokeswoman for the British firm told the BBC.

"Such projects focus on the future uses of networks and technologies and do not necessarily result in the commercial deployment of the research partner's kit in our network.

She added that BT had "a robust testing regime in place" to ensure its network remained secure.

'Finite resources'

In 2012, the US House Intelligence Committee warned that both ZTE and another Chinese firm, Huawei, posed a security threat.

Dr Levy also referenced ZTE's rival in a letter sent to the UK telecoms sector, according to the Financial Times.

"The UK telecommunications network already contains a significant amount of equipment supplied by Huawei, also a Chinese equipment manufacturer," he wrote.

"Adding in new equipment and services from another Chinese supplier would render our existing mitigations ineffective."