Shoppers with a habit of returning goods bought online to retailers will send back £1,400 of products each this year, totalling £6.6bn, a UK report has found.

Serial returners account for 11% of shoppers, but are on course to account for almost a quarter of the £27bn forecast returns this year, according to the report by the return logistics company ZigZag and the research company Retail Economics.

Serial and slow returners, who are considered to be more impulsive shoppers, often making returns out of buyer’s remorse, account for almost half of total returns.

The increase in online sales in recent years has become a costly headache for retailers, while delays in goods being returned can also make it difficult for them to manage stock levels.

More than a fifth of non-food purchases made online in the UK are now returned to the retailer.

There are also generational divides in behaviour, with younger shoppers more likely to over-order with the intention of returning a high proportion of the items. More than two-thirds (69%) of gen Z consumers said they had bought online in this way, compared with about a sixth (16%) of over-60s.

The rise of serial returners was “likely to cause alarm for retailers”, said Al Gerrie, the chief executive of ZigZag, which manages returns for companies including Selfridges, Boden and New Look.

“Led by younger shoppers, this cohort is exploiting retailers and forcing them to make more controversial and divisive actions,” he said. “Retailers will continue to clamp down on spiralling costs and returns fraud by introducing paid returns and policies that hone in on abusive returns behaviours.”

The practice of ordering extra sizes or colours only to return some items, known in the trade as “bracketing”, was admitted to by more than two-fifths of shoppers (42%).

About a sixth of shoppers (16%) admitted to having bought clothing or footwear online to use for a short period of time such as at a social event – known as “wardrobing” – while a similar number confessed to have bought clothes online to show off on social media, known as “staging”.

Retailers have been eyeing up ways to claw back some of the costs linked to consumer returns, while trying not to deter customers.

Richard Lim, the chief executive of Retail Economics, said: “Serial returners are quietly eroding retail profitability in ways many retailers are only just beginning to understand. The rise of opportunistic shopping behaviours, where many people intentionally buy large quantities of goods with the intention of returning most of them, is placing an unprecedented strain on retailers.”

The online fashion retailer Asos recently informed some shoppers that those who frequently return multiple items would be charged a fee of £3.95 unless they kept up to £40 worth of their order.

H&M, Boohoo, New Look and Uniqlo have started charging for online returns, unless shoppers take items back to retailers that have physical stores in person. Other big players are thought to be considering how to introduce delivery fees.