The independent Bar has been told to back the campaign by employed barristers for rights of audience.
Sir Sydney Lipworth QC, deputy chair of National Westminster Bank, said there was a natural empathy between in-house barristers and chambers which was potentially a significant source of work for the Bar.
If the number of barristers working in-house declined, the influence of the Bar as a whole would diminish.
It was important for the independent Bar to support the cause of their opposite numbers in commerce and industry, he said. He added that the main concern of the independent Bar was that the "dreaded" CPS would be given rights of audience.
Shell's Jyoti Munsiff said she found it "extraordinarily offensive" to hear people say that the ability of an employed lawyer to give independent advice was diluted.
She said outside solicitors and even counsel, dependent on future work, would be just as susceptible to "human weaknesses".