Gordon Brown has offered Labour MPs a free vote on controversial aspects of the new embryology bill in a dramatic climbdown designed to defuse a row over stem-cell research.

The prime minister is still refusing a free vote on the whole human fertilisation and embryology bill when it reaches the second and third readings in the House of Commons in the early summer. But Labour MPs will have the opportunity to vote with their consciences on three of the most controversial elements at the bill's committee stage. The bill will expand the scope of embryo research to account for scientific progress since the last relevant legislation was passed in 1990.