New regulations are to be introduced to curb the use of DIY kits for collecting blood from umbilical cords.
Under rules announced by the Human Tissue Authority, the collection of blood from a baby's umbilical cord will only be permitted by trained specialists at approved premises.
Cord blood is rich in stem cells and by keeping it in a bank, stored in liquid nitrogen, the blood can potentially be used at any time to treat disease. Stem cells have the capacity to develop into any kind of cell and could be used to repair or replace damaged tissue.
Thousands of couples have paid substantial sums to have cord blood samples stored for future use. But the growth of private banks, which send out DIY collection kits to couples, has worried medical authorities.
Adrian McNeil, the chief executive of the Human Tissue Authority, said: "We are introducing this regulation to make sure that the best quality samples are taken in the safest way... The worry is that if inexperienced people are involved, it will not be done at the right time and in the right way."
Under the regulations, to take effect on 5 July, all clinics will need a licence ensuring the blood is collected by trained staff following correct procedures.