In response to Archbishop Martin's request for public representatives to defend the position of the Irish Constitution, I would like to start with a quote from Bunreacht na hEireann, where in the preamble the reasons given for its adoption by the Irish people include: "that the dignity and freedom of the individual may be assured, true social order attained, the unity of our country restored."

The question for voters on June 12th is whether the Lisbon Treaty with its Charter of Fundamental Rights or the Current EU (Nice) Treaty with the Irish Constitution is more conducive to the clarity for which the Bishops call for in their pastoral letter.

We could look at many markers for comparison. A good place to start is peace in Europe and especially in Ireland. This has been achieved under the existing Treaties and national constitutions.

Probably the most important indicator for comparison is to examine the position of the weakest members of society in the current Treaty arrangements and in those proposed to the Irish voters in the referendum on June 12th.

I will start with the smallest and arguably the most vulnerable human, the embryo. Article 3 of the Charter of Fundamental Rights states that "the prohibition of the reproductive cloning of human beings" must be respected. It may surprise those who are not familiar with bioethics that the ban on reproductive cloning is to allow so-called therapeutic cloning. The European Commission made this clear in Directive 98/44/EC of the European Parliament and of the Council of 6 July 1998 on the legal protection of biotechnological inventions.

To the newly-conceived human life, the embryo, there is no difference between therapeutic and reproductive cloning, in both, the embryo dies. Increasingly in therapeutic cloning, research embryos are created in order to be destroyed.

Let's look at the situation of the child in Ireland from conception to birth. At the moment, our Constitution provides a protection for babies before birth that has prevented the legalisation of abortion in Ireland.

There is a protocol in the existing Maastricht Treaty that respects this constitutional protection. Any changes that allow legalised abortion in Ireland have to be passed by the Irish people in referendum. A national yes vote on June 12th would insert into our Constitution the 28th Amendment. A critical section of the 28th Amendment is: 1 (a) 11° "No provision of this Constitution invalidates laws enacted, acts done or measures adopted by the State that are necessitated by the obligations of membership of the European Union referred to in subsection 10° of this section, or prevents laws enacted, acts done or measures adopted by the said European union or by institutions thereof, or by bodies competent under the treaties referred to in this section, from having the force of law in the State." A similar clause passed in 1972 opened our Constitution to the then EU's treaties by placing it in an inferior position to EU legislation. This time round repeating this blank cheque to include the Lisbon Treaty with the CFR leaves us open to various risks in relation to abortion.

We will have set aside the various constitutional protections en mass should we be challenged in EU law. Where might EU law challenge our ban on abortion? One way is possibly through the Services Directive. The EU Court, in the 1991 Grogan ruling, has already decided that abortion is a service entitled to free movement like any other service. Another possibility is Article 3 of the CFR which guarantees "physical and mental integrity" a clause similar to that which allowed the Canadian Supreme Court to set aside the existing abortion laws in a landmark case twenty years ago.

With competing treaty provisions and directives, a protocol based on our Constitution which has clearly set itself aside, may not be as watertight as we are being led to believe. What will the ECJ decide in a difficult test case of competing rights? I don't know. Nor do any of our leaders campaigning for a yes vote. When you go to court you can never be sure of the outcome.

It is not unusual for us to take risks in many things, but in the life and death of our smallest human beings, I, for one, am not willing to take the risk.

Let us move on to those who have been born. Those born with a disability, or those who are later in life with a disability, or those born a long time ago and now old. Last summer I attended a euthanasia event held in the European Parliament. The morning session presented court cases and legislative practices on euthanasia across the EU. In the afternoon, an expert presented statistics on the "greying of Europe", describing the ageing of Europe's population and the coming demographic bust: one third of Europe over 65, unprecedented in the history of the world. Figures were offered on the cost of healthcare and nursing that makes caring for the elderly in a future of dwindling taxpayers look impossible. Other experts covered disability and illness and philosophised about the quality of life and discussed the legal advantages and disadvantages of voluntary and involuntary, active and passive euthanasia. By the end of the day, a speaker even opined that children should have the right to say when they die, without parental interference. Every talk in the programme was applauded by the assembled MEPs (more than I have ever seen at such a hearing), staff and NGOs and invited members of the public.

To think in Ireland that euthanasia will not be an issue is to bury our heads in the sand. I, as a disability campaigner, as an MEP representing many young and old people, and the mother of a man with profound disabilities, take the issue of euthanasia seriously. At the euthanasia event, several speakers welcomed the CFR; they claimed they were confident that given the right cases in the EU Court in Luxembourg, it would interpret the Charter terms "dignity" Article 1, "life" Article 2, "physical and mental integrity" Article 3 in a way that will lead to the legalisation of euthanasia across Europe.

I hope they are wrong. But I and the Bishops and those advocating a yes vote cannot possibly know what a future European Court will decide. All I can know is that these groups have vowed to bring cases before the court. And this is also a matter of life and death in particular, of the vulnerable. I for one am again unwilling to take this gamble.

And it is a bigger gamble than abortion, because we do not have any protective protocol and we already have precedent for euthanasia in Irish case law in the Ward Case of 1995 in which the High Court allowed a comatose woman, a ward of the state, to die by withdrawal of food and water.

I embrace the Bishops' call for greater unity in Europe but I recognise that like everyone faced with this inscrutable Treaty, it is hard to know enough about its content and impossible to predict the unknowable consequences and surprises.