The Liberal Democrats have called for an extension to Saturday's deadline to access winter fuel payments, warning tens of thousands of older people could miss out.
There has been a surge in applications for Pension Credit since Chancellor Rachel Reeves announced in July that the payment for this year would be mainly limited to those receiving the benefit.
But as of mid-November, thousands more pensioners believed to be eligible had not yet applied.
At this point there was also a backlog of 91,000 unprocessed claims, with around 9,000 being processed each week, according to the latest official figures.
The government says it has been working to boost take-up and eligible claims can be backdated.