We are very concerned about using embryos in this way, using them as a means to an end

Dr Tom Shakespeare

Scientists now hope to be able to develop new treatments for diseases such as Alzheimer's and Parkinson's Disease.

The peers' vote was welcomed by Liberal Democrat science spokesman Evan Harris, who first introduced the proposal to the Commons.

He said: "I am personally delighted - and that delight will be shared by patient groups and clinicians - that the Lords have done the morally right thing.

"That is to allow carefully regulated research on stem cells using early embryos to proceed in the search for cures for some terrible diseases.

"Large majorities in the Commons and the Lords show that the case has been made for this work."

Scientists developing treatments for a number of diseases have also welcomed the vote.

'Worrying step'

Doctor Austin Smith, from the Genome Research Centre at Edinburgh University, said the decision was good news.

"If the Lords has taken a alternative decision it would have been a devastating blow, principally for the patients who suffer from diseases like Parkinson's and Diabetes for which stem cell research offers hope," he said.

But others have expressed concern.

A leading expert on ethics in the field, Dr Tom Shakespeare, said it was a worrying step.

"We are very concerned about using embryos in this way, using them as a means to an end," he said.

"There are actually things we can do with adult stem cells, so there are alternatives to this technology.

Inquiry

"So there are very many reasons why we are going too fast and should be much more cautious about this development."

Peers voted by a majority of 120 to allow the cloning human embryos for research purposes.

They also decided that a select committee will begin an inquiry into the implications of the decision.

Some had argued that approving the regulations could be the first step towards full-scale human cloning and the ethical implications of "therapeutic" cloning had not been thought through properly.

But supporters argued that delaying research could harm people with genetic diseases.

Scientists believe that these and other conditions could be cured if they can develop new ways to regenerate or replace damaged tissue.

The best hope for this, many scientists believe, comes from stem cells present in a growing embryo.