Mishcon De Reya has told its lawyers to obtain written consent from clients in order to use Zoom for confidential conference calls.

The move, which comes amid growing concerns in some quarters about the platform's use, in response to perceived security concerns with the video-conferencing service, according to a person at the firm.

They added that the policy of written consent is one the firm is aiming to reach and not currently fully in place.

Other privacy measures have already been brought in to counter security concerns. According to a person at the firm, it has been company policy for over four weeks that all calls made using video conferencing services are password-protected.

The firm's current platform of choice for client calls is Microsoft Teams, according to Mishcon head of IT operations & security, Ned Stevanovski.

The news was first reported by Legal IT Insider.

The popularity of Zoom has grown exponentially over the last few months. The technology company recently announced its daily users had grown to 300 million, up from 10 million at the end of December last year.

However, the growth is users has also led to privacy and security concerns, for which Zoom CEO Eric Yuan apologized at the start of April.

Zoom has recently sought to upgrade its security in response to recent concerns, last week releasing the new version 5.0 of its app with enhanced encryption and privacy controls. This included new controls to prevent "Zoombombing" where people have hacked into meetings to disrupt them.

A number of lawyers have already cited new data privacy and cybersecurity risks that come with new remote-working environments, including GDPR compliance and storing of personal data.

In a statement, Zoom responded: "A large number of global institutions ranging from the world's largest financial services companies, to leading telecommunications providers, government agencies, universities, law firms, healthcare, telemedicine practices, have done exhaustive security reviews of our user, network and data center layers and confidently selected Zoom for complete deployment. We are proud to be helping these customers maintain business continuity in this challenging and unprecedented time."

One person with knowledge of the video conferencing sector added it was not surprising that law firms might seek written consent from clients to use the service as companies have to ensure their employees are using services authorized and purchased by their IT teams so they have control over what is being used and installed.