H&M is to change its UK womenswear sizes after years of complaints from customers that the clothes are smaller than expected.

“We are taking the steps to change our womenswear measurements to be in line with UK sizing, for example, the previous measurements and fit of a size 12 will now be the measurements of a size 10,” said a spokesperson for the retailer.

The existing sizing policy has frustrated many shoppers, leading one, Rebecca Parker, to write an open letter on Facebook in March. “I’ve always been a 12/14 and pleased with it, but when I tried on your jeans, I was annoyed, hot and frustrated. The pair of jeans clearly were not made for a woman who is a size 14. Why is that?” she asked.

Parker said she was not “able to pull the jeans past my one thigh”.

She went on to question how the retailer could sell pencil cases emblazoned with the word “#GRLPOWER” and T-shirts that say “SISTERHOOD” and expect women to feel empowered, while selling clothes that “do the exact opposite”.

The Swedish company has until now translated its European sizes to a lower UK size than the majority of other high street shops, meaning a European 38 would be labelled a UK 12, where in other places it would be a 10.

Although H&M has begun using the new sizing on labels, the spokesperson said: “This will be a gradual process whereby customers will experience a transition period, and are encouraged to use our sizing guides online or ask our store staff for advice when shopping.”

Customers appeared to broadly welcome the change. Parker told HuffPost UK the move was a “small victory that will have such a great impact”.