The Home Office whistleblower whose allegations sparked the row that led to Beverley Hughes' resignation said he felt vindicated by her decision.
Steve Moxon says his allegations are "just the tip of the iceberg"
Home Office official Steve Moxon said his decision to speak out had made it "worth putting my job on the line".
He was speaking as he arrived at a disciplinary hearing in Sheffield to determine if he had acted correctly.
He told newspapers that officials in Sheffield were told to waive checks on east European applications.
An internal inquiry concluded that local officials were trying to clear backlogs and ministers did not know about their decisions.
Mr Moxon said: "I feel vindicated today but I wonder who is going to take the job now.
talk of a poisoned chalice but this is more like a tanker full of cyanide.
"It was worth putting my job on the line. I don't have a very well paid job
and the pressure was intolerable."
Mr Moxon said his allegations were "just the tip of the iceberg" and said Mrs Hughes had to accept responsibility because she had been "at best incompetent".
Mr Moxon told newspapers that Home Office staff had been told to rush through as many applications as possible to make the numbers coming to Britain less dramatic when the EU expanded.
He said the change affected migrants from the eight eastern European countries due to join the EU in May.
After Mr Moxon's suspension, the Home Office admitted some checks had been waived, but said it was local officials trying to clear a backlog rather than ministers seeking to massage the figures.
The Home Office's admission was accepted by the independent inquiry.