Thieves stole computer hardware holding barristers' contact and bank account details from the offices of the Bar Council, a spokesman said today.
Four back-up hard drives and a laptop were taken in the raid on the building in Holborn, central London, on Friday, which also houses the Bar Standards Board.
Among the information held on the disks was the contact details of over 12,000 practising barristers plus bank account numbers and sort codes from 3,000 Direct Debits for membership fees.
Also stolen were 1,500 computerised complaints records including names and contact details of barristers, complainants and witnesses.
A spokesman said the contact details were routinely published on websites and directories. The bank data did not include passwords, pin numbers or card details, he said.
All the information was protected by two or three levels of security, including encryption and password protection, and could not be accessed readily, he said.
Police were called on Saturday morning when the break-in was discovered and officers are investigating the thefts.
Bar Council chief executive David Hobart said: "I am sorry that, as a result of this burglary, barristers and some members of the public have had data stolen from the Bar Council office in Holborn.
"At present the signs are this was a random burglary, but to be sure we will have to wait for the outcome of the police investigation.
"I want to reassure anyone who may be concerned that the stolen data is correctly and safely protected, and I am confident that no one will suffer loss as a result."
:: A Bar Council helpline has been set up on 0207 611 1418 for anyone with questions about the thefts.