MPs will vote on decriminalising abortion tomorrow with the Commons expected to back the biggest change to abortion law in Britain for half a century.

If approved by MPs women would no longer face prosecution if they aborted their own baby based on its sex, after the legal limit of 24 weeks, or without approval from doctors.

The vote is shaping up to be fractious with two Labour MPs who are both seeking to decriminalise abortion competing to have amendments that will radically alter the law selected.

Currently abortion is a criminal offence in England and Wales unless it takes place before 24 weeks into a pregnancy and with the approval of doctors. There are limited circumstances allowing a woman to access an abortion after 24 weeks, including when the mother’s life is at risk or the child would be born with a severe disability.

Six women have appeared in court in the last three years charged with ending or attempting to end their own pregnancy - a crime with a maximum sentence of life imprisonment.