Breastfeeding mums are sharing their milk through free, online sites, with one in 50 admitting to already taking part, according to a survey of 2,012 mums, by Netmums.
The study also found almost half (44%) of breastfeeding mothers said they'd consider offering their milk.
Netmums editor-in-chief Anne-Marie O’Leary said: "Milksharing is the ultimate milk of human kindness.
"In a world where almost everything is now commercialised, it’s wonderful to see families coming together to help and support each other for free."
The online "milksharing" services match mums with other mums who have milk to give away in their local area. These sites, according to Netmums, are run through Facebook and other social media sites by volunteers.
The reasons people cited for using the "milksharing" services included: because they were too unwell to breastfeed after giving birth (22%), they had low milk supply (a further 22%) or because they had a medical condition which left them unable to breastfeed (16%).
An example of an online "milksharing" service is 'Human Milk 4 Human Babies' - a Facebook page with nearly 9,000 likes that promotes sharing breast milk in the community.
Celebrity backers of this trend include Hollywood actress Alicia Silverstone, who recently set up her own milksharing site, ‘Kind Mama’.
Two in five mums admitted that as well as donating milk, they would actually breastfeed a stranger's baby and one in 25 had already breastfed a child for a friend or family member and 8% had breastfed a stranger’s child.
The survey revealed 14% of mums produced much more milk than their baby needed, which was a big factor contributing to why they donate.
O'Leary added: "Everyone involved - from the mums donating milk to those running the sites - give their time and effort without charge to ensure babies get a healthy start in life.
"The trend may be new but it’s already touching people’s lives and making a significant difference which will last the families it helps forever."
However not everyone involved in "milksharing" gives their time and effort without charge, according to Netmums some sites are taking advantage of desperate parents by charging for the milk, and also selling milk to bodybuilders and other groups who do not need it.
As a result, one third of mums believe the sale of breastmilk should be banned and it should only ever be offered for free to families in need.
The findings come after a controversial image was posted on Facebook showing one mum breastfeeding her son and friend's son.
The mother in the photo said: "Breastfeeding my friend's son came naturally to me. I started babysitting him when he was five months old and the first time she dropped him off to me I asked permission to nurse him, since I was already nursing my three-month-old.
"She responded with an enthusiastic yes, because he was having issues with the formula his previous sitter had been giving him."
"The most important thing is that the mothers are comfortable with it. There is a very small risk of infection and they may want to be sure the person feeding their baby isn’t smoking or taking drugs.
"Receiving milk from official, regulated milk banks is very safe as they ensure donations are collected and stored to the highest standard. The UK Association for Milk Banking provides tested and pasteurised breastmilk from rigorously screened donors. This can be a life-saving service for premature and sick babies.
"However there are no guarantees when buying breastmilk online from someone you don’t know. Research in the US found that samples sent following internet contact often had a higher level of bacterial contamination and there is a theoretical risk of viral infection.
"More information about milk sharing and milk banks is available on our website."
According to the European Milk Bank Association (EMBA), every year in the UK more than 1,500 donors provide over 6,500 litres of milk to regulated milk banks, which goes to feed premature babies and babies recovering from gut surgery.
The EMBA also state thatmums should be away of the risks of sharing milk.
In a statement, they said: "The main risks of sharing milk are that it is contaminated with pathogenic bacteria or that it contains viruses such as HIV, Hepatitis or HTLV (Human T Lymphotropic Virus).
"Harmful bacteria ingested in large quantities through breastmilk may lead to severe infections including septicaemia. Viruses such as HIV and HTLV in breastmilk can cause serious illnesses, some of them manifesting several years after contamination.
"We advise all parents to be aware of the risks involved in feeding a baby with another mother’s milk and before doing so to consult a qualified healthcare professional such as a paediatrician, neonatologist or hospital infant feeding specialist."
A worrying consequence of the rise in these milk-sharing sites is those taking advantage of the milk online.
The study revealed some sites are taking advantage of desperate parents by charging for the milk, and also selling milk to bodybuilders and other groups who do not need it.
As a result, one third (33%) of mums believe the sale of breastmilk should be banned and it should only ever be offered for free to families in need.
What are your thoughts? Would you be happy to donate your breastmilk? Let us know in the comments section below.