The problem worsened in 2018, when only 209 out of 5,500 requests for asylum seekers to be returned were completed, while the UK accepted 1,215 migrants.
The figure comes in stark contrast to the 131 who were transferred into the UK in 2015, when 510 asylum seekers had been transferred out.
Labour MPs have also been left divided on whether Ms Mahmood or Mr Burnham are correct.
GB News has approached the Home Office for comment.
