MPs who probed the board earlier this year were told it had taken three years for the board to complete its staffing.
Lack of staff had caused the backlog, with some cases taking over a year to resolve.
Its chair Sir Anthony Holland told MPs the board had had problems in recruiting staff in London because of the salaries it could offer.
This was set up by chancellor Gordon Brown to move these jobs to cheaper locations than London (LGC, 15 April 2003).
The move means 120 board staff in London would have to be offered redundancy terms if they declined to move to Manchester by 2007.
The board would have to replace them from scratch and train new staff.
A spokesman said: 'Some people will relocate and we will recruit new staff too. The move will be done over a period of time and we do not expect it to cause any backlog of our work.'