David Cameron's official spokesman sidestepped repeated questions from reporters whether the Prime Minister was "confident" that Universal Credit would be delivered on time and on budget.
He said: "The department is working to the 2017 timetable. That is the timetable that the department continues to work to."
Pressed on whether it was right for ministers, rather than senior officials, to take responsibility for failings in implementing major policies, the No 10 spokesman said the Prime Minister had previously insisted that "everyone has to take their responsibility."
More top news
The Hollywood star refused to appear on ITV's Good Morning Britain because of host Piers Morgan's comments about the women's marches.
The former Ukip leader has torn into the Labour leader as he backed his successor Paul Nuttall to claim the vacant Stoke Central seat.
The man, in his thirties, was found with stab injuries on the upper deck of a bus in Handsworth, Birmingham, on Monday night.