Only 6,000 more older people are receiving pension credit since ministers cut the winter fuel allowance and the backlog of claims is growing.
There are 53,400 claims waiting to be assessed as officials struggle with a rise in applications as winter weather sets in.
The bulk of pension credit applications since the summer have been rejected, according to figures released on Tuesday.
• Rachel Reeves: Trickle-down era is over, but winter fuel cuts here to stay
Labour announced this year that winter fuel allowance will be given only to those receiving pension credit, rather than to all pensioners. This change was expected to mean that ten million people lost the benefit. Pension credits are available for those whose income is less than £11,344 a year,