The warning was made amid concern among City law firm bosses that younger lawyers are missing out on key experience by working remotely.

A&O Shearman, the product of a merger between Allen & Overy in London and Shearman & Sterling last year, sent the memo to associates in its City office in the past few weeks, according to The Times.

The memo suggested bonuses could be withheld from junior lawyers who failed to attend the office for at least 60 per cent of a standard working week.

The London office of US firm Sullivan & Cromwell recently told staff to return to a full five days in the office. Paul Weiss, another US law firm, introduced a policy of a minimum of four days per week in the office.

Their moves follow those of a group of US law firms that have mandated at least four days in the office. They include Davis Polk, Skadde, Ropes & Gray, Weil, Gotshal & Manges, and Vinson & Elkins.