The pensions minister Baroness Ros Altman has blasted Iain Duncan Smith's resignation saying she believes it's really about the EU referendum.
"I’m particularly saddened that this really seems to be about the European referendum campaign rather than about DWP policy," Altman said in a statement.
Duncan Smith, who unexpectedly resigned as work and pensions secretary on Friday evening, blamed pressure from the Treasury to make cuts to disability benefits for his decision in a scathing letter against the chancellor George Osborne and Prime Minister David Cameron.
However, Altman delivered a fresh blow to Duncan Smith, claiming he was "incredibly difficult to work for".
"From a personal perspective, for months I have been silenced by him and what I have said has been strictly controlled. I have had to accept that this is part of being in Government, but am therefore horrified to see him abuse the freedom to take sides the Prime Minister has generously offered to ministers. In particular, I was astonished that he attacked his own government for producing what he called 'dodgy dossiers' on the EU situation, which simply sought to set out the facts about this vital issue for our country’s future.
"He seems to want to do maximum damage to the party leadership in order to further his campaign to try to get Britain to leave the EU. As far as I could tell, he appeared to spend much of the last few months plotting over Europe and against the leadership of the party and it seemed to me he had been planning to find a reason to resign for a long time. I have found him exceptionally difficult to work for. It has been a hugely challenging time for me as he was preventing me from speaking to the public and has often been obstructive to my efforts to resolve important pension policy issues such as on women's pensions."
However, employment minister Priti Patel and parliamentary under-secretary of state Shailesh Vara, both working in the DWP, have defended Duncan Smith's time at the department.
"I have to say I'm surprised by Ros's comments" Vara said in a text to Duncan Smith, the Times Red Box reports.
Duncan Smith is due to appear in the BBC's Andrew Marr show on Sunday morning in his first media appearance since his resignation.