A cross-party group of peers backed by the Law Society and the bar called on the government to amend its Investigatory Powers Bill to protect the right to communicate with a lawyer in confidence.
The bill, which the government says will simplify the rules governing state interceptions of communications, began its committee stage in the House of Lords today.
During the bill's passage through parliament, professional bodies have warned of the lack of protection for privileged material, calling for an explicit ban on the targeting of such information.
The committee will today hear an amendment to that effect proposed by cross-bencher Lord Pannick (David Pannick QC, pictured) with the backing of the Law Society and Bar Council.
Pannick said: 'The government needs to add to the bill clear protection for the legal professional privilege of clients to obtain advice in confidence. As the courts have repeatedly recognised, the ability to obtain advice in confidence is central to the rule of law.
'Clients are not going to seek advice, and be frank with the solicitors and counsel advising them, if they fear that someone else is listening in.'
Law Society president Jonathan Smithers described legal professional privilege as fundamental to the justice system.
'Our legal system functions only when people can speak to their lawyer without fear of their communications being intercepted and confidentiality broken.'
He said that the government is working constructively with the legal profession to address the issue.