But important questions remain about the viability of animals produced by this method, and about the possibility that they may be more prone to cancers and that flocks of them might have lowered resistance to natural diseases.
The breakthrough, the first time such cloning has been achieved in the world, was the work of scientists at the Roslin Institute near Edinburgh and the biotechnology company PPL Therapeutics, and builds on work done there last year.
The first of the cloned sheep, Dolly, was born a few weeks ago - but comes from an animal which is six years old. That means that its genes have already been damaged by cosmic rays and environmental toxins, meaning the sheep could develop cancers abnormally early.
Also, a genetic "fuse" on the chromosomes, called the telomere - which burns down one by one step every time the cell divides - will have shortened so radically that the animal could die abruptly. Sheep on farms normally have a lifespan of less than 10 years.
Dr Ian Wilmut, who led the research team at the institute, said last night that there was no data yet about the effects of genetic damage and telomere shortening.
The immediate application of cloning will be to study ageing, cancer and genetics, and to produce medicines. But it opens up the possibility of a bizarre world in which people can be copied and animals are "made" on a production line - as described in Aldous Huxley's novel Brave New World.
The scientists started with cells taken from an adult animal and slowed down the division of the chromosomes in the nucleus. They then took unfertilised egg cells, removed their nucleus - which contains the genetic material of the egg's mother - and inserted the nuclei of the original adult cells.
This cloned cell was implanted in a ewe, and produced a total of eight lambs. Both male and female sheep can be produced by the process.
In theory, the same principle could be used with human cells and eggs. However, it would be illegal to clone a human under the present law, and attempts to clone animals can only be performed under licence from the Home Office.
Dr Wilmut said: "The idea of cloning humans is just fanciful. All of us would find it completely unacceptable to work with human embryos. It's important that inappropriate use of this technology is prohibited.
"We shouldn't throw out the baby with the bathwater. Britain should be celebrating this advance which offers commercial opportunities for companies here and potential healthcare products for British patients."
Scientists concerned with ethical issues said yesterday that it may be necessary to introduce laws against the cloning of animals for "production purposes".
Dr Donald Bruce, a research chemist who chairs a committee on science, religion and technology for the Church of Scotland, said: "I don't have any objections to the genetic modification, to the experiment ... But to turn them out like a production line of widgets seems to lose something of the individual dignity of the animal, to lose respect for it."
Last year, scientists at the institute produced cloned sheep by implanting cells taken from an embryo into an egg cell. That produced mixed results, with unusually large animals and a number of deaths at birth. The new technique appears to be more efficient. Only one of the clones died at birth, and that showed no signs of infection or abnormality.
PPL Therapeutics, which has bred genetically engineered sheep able to produce human proteins in their milk, said it was "a major scientific advance".Reuse content