Three Addison Lee minicab drivers who helped lead a protest outside Carlyle Group have had their contracts terminated, in a further escalation in the conflict between the drivers and the private equity group.

The three were chosen by fellow Addison Lee drivers to voice concerns to the senior management of Addison Lee, majority-owned by Carlyle, about a number of changes the company has made in recent months to working and pay conditions, according to people familiar with the matter.