BBC News Online looks at the pros and cons of setting up a stem cell bank.

What are stem cells?

Stem cells are the "master cells" of the human body that have the potential to develop into almost every other type of cell.

They can be grown in the lab, and, in theory, could be made to develop into the likes of nerve tissue, blood, heart muscle and even brain cells.

Scientists believe stem cells might one day provide us with a ready supply of tissue for transplant operations.

At the moment, embryos that are not used are just discarded

Medical Research Council

Cells would be implanted into our bodies to repair the damage caused by illnesses like heart disease.

Ultimately, however, it may be possible to persuade stem cells to grow into complete organs.

Where do they come from?

True stem cells come from human embryos, but they can also be found in adult tissue.

It is not clear whether so-called adult stem cells have the flexibility of embryonic cells to grow into other cell types.

Research has shown for example that adult bone marrow cells can become liver cells.

But scientists believe we may need embryonic stem cells to get the full range of cell types for medical treatments.

Why have a stem cell bank?

The bank would collect thousands of cells from human embryos and adults for research into medical conditions including Parkinson's and Alzheimer's.

Couples who have undergone fertility treatment would be asked to donate any spare embryos for harnessing stem cells.

"At the moment, embryos that are not used are just discarded," says the Medical Research Council (MRC), which is behind the plans.

It says embryos would only be used in the bank with the full informed consent of the couples involved.

Under British law, scientists are allowed to conduct research on embryos up to 14 days old.

At this stage an embryo is a small bundle of cells about the size of a pin-head.

What are the objections?

The plans have been criticised by Pro-Life groups who object to the use of human embryos.

They argue that the research is immoral and are strongly opposed to the idea of developing medical treatments from embryonic stem cells.

Concern has also been raised that couples receiving infertility treatment may be put under pressure to donate spare embryos for medical research.

The Human Fertilisation and Embryology Authority, which regulates embryo research, says strict guidelines are in place at clinics to protect patients.

What happens next?

The bank must be given full ministerial approval, which is expected next month.

It will be managed by the MRC, under tender.

The bank will be operated without any vested commercial interest, says the MRC.

A number of charities are believed to have expressed an interest in running it.