No impact assessment was carried out on how the decision to strip around 10 million pensioners of a winter fuel payment will affect them, Sir Keir Starmer has admitted.
The allowance, which is worth up to £300 and will now be means-tested, was taken away to help fill a "£22bn black hole" in the government finances.
An estimated 10.8 million pensioners benefitted from the payment last winter, while only 1.5 million are expected to do so this year.
Sir Keir, on his way to Washington DC, told reporters: "There isn't a report on my desk which somehow we're not showing, that I'm not showing, as simple as that."
While an impact assessment isn't legally required, a Downing Street spokeswoman said some statistical work had been done, but no work had been done on what impact the change might have on vulnerable pensioners.
The spokeswoman added: "The Government will be ensuring that those who are most vulnerable and should be receiving support are receiving it, and that's why there is a huge effort to try and convert people onto pension credit.
"And also, we want people to be applying for the wider support, which is also there for the most vulnerable."