It was revealed yesterday that 700,000 people are awaiting benefits assessments as Hemel Hempstead MP and disabilities minister Mike Penning blamed the firm responsible for carrying them out.
It was the job of Atos to if whether people are fit to work - a decision used to decide if they are entitled to employment and support allowance (ESA).
But there are now 394,000 new claimants and 234,000 waiting reassessment in limbo for the assessment to be carried out.
The number of people awaiting the assessment has more than trebled to 712,000 in four years.
On top of that, a third of Atos assessment decisions are overturned on appeal.
Mr Penning, speaking at the Work and Pensions Select Committee, said: “I don’t think Atos had the capacity to do what was asked.”
A further 84,000 are people still on incapacity benefit who have not yet been moved over to ESA.
Mr Penning admitted the government failed to meet its own deadline of moving these people onto the new benefit by April, and they are still awaiting assessment.
He said a decision in March to end Atos’s contract early was based on the fact he had lost faith in the firm.
He said a new contractor - expected to be appointed in early 2015 - would not be chosen on cost alone but on its ability to carry out the assessments in a timely and proper fashion.