MPs have voted to push back the boundaries of science by allowing radical embryo research including the creation of human-animal hybrids.

Following a landmark Commons vote, Britain will become one of a handful of countries in the world to encourage ground-breaking research by implanting human cells into an egg taken from an animal, usually a rabbit.

Pro-life MPs warned that the step could lead to the creation of half-human, half-ape "humanzees" or "minotaurs" - a claim denied by the Department of Health.

Hybrids - called "admixed embryos" by the scientific community - are banned in at least 21 countries, but scientists believe that they could be used to find cures for dozens of serious conditions, from heart disease to dementia.

MPs voted overwhelmingly in favour of the Human Fertilisation and Embryology Bill after being told that it could revolutionise the lives of hundreds of thousands of people, bringing to a close one of the most bitter Parliamentary wrangles of recent years.

As well as embryo research, there were further clashes over proposals which will give lesbians equal access to fertility treatment, and moves to allow parents with a sick child to create a "saviour sibling" to be harvested for cells to cure their older brother or sister.

Urging MPs to back all of the measures, Dawn Primarolo, the health minister, said: "One in seven couples need help with fertility treatment, 350,000 people live with Alzheimer's, every week there are five children born and three young people die from cystic fibrosis - all issues that this Bill addresses.''

Gordon Brown, whose youngest son suffers from cystic fibrosis, attended the Commons in person to vote for the proposals, having urged MPs to back the move.

While Conservatives and Liberal Democrat MPs were granted a free vote, meaning they could vote according to their conscience, Labour were required to back it, leading a small group, including a number of Catholics, to defy the Prime Minster and rebel.

Scientists want to use animal cells because of a shortage of human eggs for use by researchers.

A handful of hybrid embryos have already been created by researchers at Newcastle University, but scientists asked Parliament to regulate the practice amid fears that they could be open to legal action.

Catholic Church leaders have described the use of hybrid embryos as ''monstrous,'' while other campaigners said that Britain would become a "rogue state" if the measure was passed.

The vote followed a passionate debate in the House, with MPs expressing concern about the mixing of human and animal cells.

Nadine Dorries, a leading pro-life Tory backbencher, warned that the new law could lead to a "humanzee," adding that it was ''serious, sinister and absolutely, ultimately ridiculous'' not to explicitly outlaw such a procedure.

Jeffrey Donaldson, a Democratic Unionist, said: Jeffrey Donaldson added: "The image that people have in their heads and the image that they find most abhorrent is of scientists producing GM babies or cloned adults or minotaurs.''

John Hayes, Conservative MP for South Holland, said: "Science matters, but morals matter more."

The Bill was passed overwhelmingly, by 355 votes to 129.

But a succession of MPs urged the Speaker to intervene as the Government limited the debate to just a few hours, meaning that many of the main provisions of the Bill, including saviour siblings and IVF for lesbians, were not debated.

There was also anger from a number of MPs and campaigners after ministers moved to block an attempt to include discussion on access to abortion services as part of the debate.

The Government was accused acting in a "shabby" and "cynical" way, after passing a motion which blocked a series of amendments which would have liberalised the abortion laws, including bringing legal terminations to Northern Ireland for the first time.

Julie Bentley, Chief Executive, of the Family Planning Association, said: "We are extremely dismayed. The women of Northern Ireland are the real victims in today's events in Parliament. They have been badly let down by the UK Government."

But Ms Primarolo said that the Bill represented a: "good deal for science and a good deal for society."

She added: "The kaleidoscope of science is coming to a rest and careful consideration of the Bill has been given in this chamber."

Ruth Kelly, the former transport secretary and a member of the hard-line Catholic group Opus Dei, defied Mr Brown by rebelling in her first Commons vote since standing down from the Government earlier this month.

Most countries have yet to legislate on animal-human hybrids, meaning it is difficult to pin down where experiments have taken place.

Hybrids are known to have been created in China and America.

The Human Fertilisation and Embryology Authority says that such experiments are banned in Australia.

Canada has recently voted to allow them, while India is currently considering the move.