The organisation, which has yet to be named but might be called Agenda, announced shortly before the merger that it planned to reduce its workforce by 310 posts, from 2,750 to 2,440, which represents more than a tenth of all employees.
Figures released last week revealed that 288 staff have left.
There have been 67 compulsory redundancies, 113 voluntary redundancies and 108 people who have left through staff turnover.
A spokesman for the merged charity said the organisation was "in the final stages of removing the inevitable duplication of roles.
"We have sought to minimise the need for compulsory redundancies as much as possible," he said.
"Before the merger, many vacant posts were left unfilled. After the merger, all staff were offered the option of applying for voluntary redundancy and we have sought to redeploy staff whose roles are no longer required."