Research from environmental charity Hubbub showed that as many as 95 per cent of them are made using plastic and two out of five Christmas jumpers are worn just once.

In a survey of 3,008 UK adults it also found that only 29 per cent of people realised that most Christmas jumpers contain plastic.

The most common plastic fibre used is acrylic, which was found in three quarters of the jumpers tested, with 44 per cent made entirely from acrylic.

A study by Plymouth University found that acrylic was responsible for releasing nearly 730,000 microfibres per wash, five times more than polyester-cotton blend fabric, and nearly 1.5 times as many as pure polyester.

Hubbub recommends several actions that the environmentally minded can take to reduce the impact of seasonal clothing.

Consumers are firstly reminded to check what they own and wear last year’s jumper rather than a buying a new one every time Christmas comes around. Swapping with a similarly sized friend or housemate is another way get a new look with minimal effort and no cost.

Buying second-hand is another option as they are typically worn only a few times by the original owner.

It estimated UK shoppers will buy 12 million jumpers this festive season, despite already having 65 million stashed away from previous years.

Hubbub’s Sarah Divall said: “We don’t want to stop people dressing up and having a great time at Christmas, but there are so many ways to do this without buying new.

“Fast fashion is a major threat to the natural world and Christmas jumpers are particularly problematic as so many contain plastic. We’d urge people to swap, buy second-hand or rewear and remember a jumper is for life, not just for Christmas.”

In November consumers were warned to steer clear of wrapping paper and Christmas crackers, which typically contain lots of unrecyclable plastics.

Last year E&T looked at how people can celebrate Christmas without plastic including plastic-free gift ideas, decorations and food.

Research from environmental charity Hubbub showed that as many as 95 per cent of them are made using plastic and two out of five Christmas jumpers are worn just once.

In a survey of 3,008 UK adults it also found that only 29 per cent of people realised that most Christmas jumpers contain plastic.

The most common plastic fibre used is acrylic, which was found in three quarters of the jumpers tested, with 44 per cent made entirely from acrylic.

A study by Plymouth University found that acrylic was responsible for releasing nearly 730,000 microfibres per wash, five times more than polyester-cotton blend fabric, and nearly 1.5 times as many as pure polyester.

Hubbub recommends several actions that the environmentally minded can take to reduce the impact of seasonal clothing.

Consumers are firstly reminded to check what they own and wear last year’s jumper rather than a buying a new one every time Christmas comes around. Swapping with a similarly sized friend or housemate is another way get a new look with minimal effort and no cost.

Buying second-hand is another option as they are typically worn only a few times by the original owner.

It estimated UK shoppers will buy 12 million jumpers this festive season, despite already having 65 million stashed away from previous years.

Hubbub’s Sarah Divall said: “We don’t want to stop people dressing up and having a great time at Christmas, but there are so many ways to do this without buying new.

“Fast fashion is a major threat to the natural world and Christmas jumpers are particularly problematic as so many contain plastic. We’d urge people to swap, buy second-hand or rewear and remember a jumper is for life, not just for Christmas.”

In November consumers were warned to steer clear of wrapping paper and Christmas crackers, which typically contain lots of unrecyclable plastics.

Last year E&T looked at how people can celebrate Christmas without plastic including plastic-free gift ideas, decorations and food.