Dr Harris is to table the amendment to the bill himself

Liberal Democrat Dr Evan Harris has called on the government to allow a free vote on an amendment to the Human Tissue Bill.

The amendment would replace the current "opt-in" system for organ donations with an "opt-out" - or presumed consent - system.

Dr Harris, a former hospital doctor, made the call after the idea received support in a BBC Radio 4 listeners' poll on ideas for new legislation.

The MP for Oxford West and Abingdon said he had the backing of patient groups, such as the National Kidney Federation, as well as the BMA.

He added: "Hundreds of patients die each year while waiting for an organ transplant.

"These tragic deaths, often of young people, are entirely avoidable since hundreds of organs are lost each year following deaths of potential donors who would have wanted them to be used to save or transform the lives of others, but who never opted in through the donor card or organ register and whose relatives refused permission, unable to second guess their loved ones' wishes.