David Cameron has sidestepped questions over whether tax credit claimants will still be worse off when measures to soften the impact of reforms are announced next month.
The Prime Minister repeatedly refused to say if the some of the country's poorest households would still lose out under the reforms aimed at cutting £4.4 billion off the welfare bill.
Labour leader Jeremy Corbyn told the premier "people are very worried about what's going to happen to them" and called on him to make a cast-iron guarantee that claimants would not be hit financially.
Mr Cameron said: "We will set out our new proposals in the Autumn Statement."