The survey found girls are receiving an average of 37p a week less than boys, at £5.79 and £6.16 respectively, which amounts to a £19.24 shortfall over a year.
Last year saw the average overall amount rise to £6.25 from a seven-year low of £5.89 in 2010 while the gender gap had also been closing, with girls earning 32p per week less than boys compared to 40p the year before.
Halifax suggested that the changes reflected a widespread strain on family finances.
The poll also found that 77% of eight to 15-year-olds receive pocket money, down from 83% in 2011, 43% of children think they should get more money, 67% save at least a quarter of their pocket money and 40% keep their money in a bank or building society account.
Children in London and th South East receive the most pocket money at £7.34 a week while those in the East Midlands get the least at £4.44.
While 32% of children have never talked about pocket money with their peers, 28% believe they get the same amount as their friends and just 8% believe they get less.
Halifax calculated that a week's pocket money in 1987 would have bought five Twirl bars at 22p each, whereas children could now buy 10 bars a week at 60p each.
Richard Fearon, Halifax head of savings, said: "It is encouraging to see that over two-thirds of children are still saving at least a quarter of the money they get despite the fact that the amount of pocket money they receive has fallen.
"Pocket money is often the first opportunity children have to manage money and it gives them valuable insight into the benefits of both short and long-term saving.
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