Mr Hoon told a newspaper MPs would be able to use special "standing orders of the Parliamentary Labour Party" to absent themselves from upcoming Commons votes on the legislation.

"Nobody will be required to vote against their conscience," he said.

The Bill, which includes measures to allow mixing of human and animal embryos to create hybrids and allowing lesbian couples to register as joint legal parents of a child born through fertility treatment, has completed its third reading in the House of Lords and will soon be entering the Commons.

The announcement comes as more than 100 scientists, lawyers, philosophers and theologians signed a letter to another newspaper saying the Government and opposition parties should not force MPs to follow a party line in the votes.

The 108 scientists, lawyers, philosophers and theologians who signed the letter said that although they did not hold "a single common view" on the content of the Bill, they all believed that "political parties should not erode the principle of a 'conscience vote' on controversial bioethical legislation".

Reports said that Labour MPs who feel strongly will have to write to the Chief Whip and explain why they cannot vote in favour.

Mr Hoon said: "This is important legislation and whilst I entirely respect the strong moral sensitivities of colleagues there are also strong moral sensitivities in relation to research into a number of appalling diseases and conditions.

"I accept that the Catholic Church has a view and a role. But part of the frustration is that there hasn't been the coverage about what is possible, what this does and why we are doing it. One of my closest friends here, Kevin Hughes, who I was elected with, died of motor neurone disease. I still feel his loss now. It's the most horrendous disease."

The Bill seeks to bring the regulatory framework for fertility treatment and embryo research up to date with advances in science.