Barclays is understood to have appointed Grass Roots to deliver venue-finding services globally for a three-year term.
The loss for Zibrant follows the upcoming departure of Lex Butler, business development director, who will be leaving in August to launch a new events agency. Earlier this year, P&MM's events division was merged with Zibrant Global Events to form Zibrant LIVE.
Barclays said it would not comment on appointments to its events roster.
Zibrant was unavailable for comment, while Grass Roots declined to comment.