Major reforms to the legal system governing those who have lost mental capacity are proposed by this Bill.While many campaigners expected the Bill to appear in the 2003 Queen's Speech, the fact that it did not reflects its controversial nature.

MPs and peers have already begun to express their dismay at provisions allowing for a patient to make an "advance decisions" to cease a medical treatment or even nutrition.The Bill, still in draft form, sets out to replace what Lord Irvine, former Lord Chancellor, described as a "confusing and fragmented" legal status quo.

It has taken 14 years and numerous stages of consultation for the Bill to reach its current form.

A joint committee conducted pre-legislative scrutiny of the Bill and produced a largely favourable report - though there was difference of opinion - in late November.

An estimated two million people would be covered by the definition of incapacity contained within the Bill. This wide patient population would include dementia sufferers, people with brain injury, and people with diagnosed mental illnesses.

The Bill will introduce a legal framework giving a nominated individual the power of attorney over a patient's affairs. This would not only include the right to make financial decisions, as is currently the case, but also the right to decide what sort of treatment, if any, a patient should receive.

In order to prevent exploitation, the Bill will propose safeguards such as a new court of protection, the criminal offence of "abusing the power of attorney", and a regime of "public guardians" that would investigate reported offences.

The draft Bill does contain an additional provision that was not contained in the 1999 white paper Making Decisions, on which it is based: it allows a capable person to make an "advance decision" to refuse treatment, or food and drink, when they later become incapable.

In other words, someone who is suffering early stage dementia could make a legally-recognised decision that they would refuse artificial nutrition if they were in a persistent vegetative state.

Anti-euthanasia groups have described this as de facto euthanasia and are preparing for a drawn out campaign when it is introduced into parliament.