Former South Australian senator Nick Xenophon must sign up to the foreign influence register because of his legal work for Chinese telecommunications company Huawei, Parliament's Intelligence and Security Committee chairman Andrew Hastie has demanded.

Mr Xenophon returned to his legal career advocating for Huawei, which the Australian government has banned from building the 5G and national broadband networks on security grounds.

Former senator Nick Xenophon and former ABC foreign correspondent Mark Davis outside the Supreme Court in Sydney. Credit:James Alcock

The former parliamentarian defied a similar call made by the junior government Senator James Paterson last year, claiming his law firm's work for Huawei does not constitute working for a foreign power.

Mr Xenophon has vowed to go after Huawei's critics using Australian laws to contest what he says are "false and unsubstantiated" comments about the company's security credentials and claims that it has links to the Chinese state.