Barclays general counsel Mark Harding said the demands would now be rolled out for every firm across the 10 specialist panels the bank uses. Some US-based multinationals already request diversity statistics, but Barclays is understood to be the first UK company to take the step. A poll by The Lawyer of some of the 25 firms on Barclays' panels brought mixed results.
Slaughter and May practice partner David Frank said: "It's not unlike asking about a firm's pro bono work. It's an increasing trend and, if the client demands it, they will get what they want."
While Frank said his firm had the statistics to hand and had been asked for them before, Withers partner John Riches said: "I have to show my ignorance and confess I don't know what you mean when you say 'diversity'."
Slaughters is on Barclays' structured capital markets panel, while Withers is on the wealth structuring and fiduciary panel.
As chair of the General Counsel 100 Group, a committee of legal heads from FTSE100 companies, Harding is expected to bring the issue to the top of the agenda for in-house departments and their law firms.
He said it was "at least a five-year project" to bring diversity levels up to an acceptable standard.
"The truth is, it won't be fixed until we're getting a good mix coming through our law schools and into the major law firms," he said.
Harding admitted that his own legal function, which has established an equality and diversity committee, failed on ethnic diversity, although he was confident the company had a good gender mix.