THE 1983 abortion referendum makes it "absolutely clear" that the mother of a child is the pregnant woman who gives birth to it, the Government has told the High Court.

In the closing stages of a landmark action involving a married couple who are the genetic parents of twin girls born to a surrogate - the sister of the wife - the Attorney General has insisted that the birth mother is the only mother for the purposes of Irish law.

Senior Counsel Mary O'Toole, for the Attorney, said that the definition of the mother is set out in the Constitution following the 1983 anti abortion referendum.

But the lawyer for the State said it is open to the legislature to put in place laws to allow surrogacy arrangements to be regulated so that the birth mothers constitutional status and rights are respected.

The Office of the Attorney General was pressed this morning by Ireland's most senior family law judge about whether the Government intended to legislate for surrogacy which is included in the Fine Gael\Labour Programme for Government.

"Is there a serious prospect of legislation?" asked High Court Judge Mr Justice Henry Abbott who heard that the birth mother of the twins is entitled, as of right, to custody of the twins who are living with their genetic parents.

The Attorney said that the married couple - who want to be registered as the parents of the twins on their birth certificates - had not yet explored other avenues including adoption.

The genetic father has not yet applied to be a guardian of the twins.

And the State said it would not hinder any attempt by the genetic father to apply to be a legal guardian of the twins.

The High Court heard that the birth mother was judicially separated at the time of the birth and - still regarded as married for the purposes of the Constitution at the time of birth - which could create potential "risks" and "procedural hoops" if the genetic parents wished to adopt the twin girls.

Closing the case for the Attorney, Ms O'Toole said that the birth mother is the person conferred with motherhood “directly by the people" courtesy of the poll which fell for consideration by the Supreme Court in the divisive 1992 X case.

No other construction of 'mother' is possible in Irish law because of the 1983 amendment, the Attorney General argued.

Judge Abbott, however, said it could hardly be said that there was any majority view taken on surrogacy at that time.

"It is the birth mother that is protected under the Constitution and it is the birth mother to whom rights inhere," said Ms O'Toole, adding that it could only have been contemplated at the time of the abortion poll that motherhood was "inextricably linked" with pregnancy.

There is no other way of looking at it (motherhood), said Ms O'Toole who said that the courts had no option to consider the term 'mother' in various statutes as the birth mother.

The State could, however, put in pace laws to allow surrogacy arrangements to be regulated so that the birth mothers constitutional status and rights are respected and there is an ability to transfer those parental maternal rights to others based on a surrogacy arrangement.

"But that notion engages a whole range of social and political issues that are matters for the legislature".

"A mother for the purposes of the Constitution is a birth mother, no other is contemplated...That is what mothers are at a constitutional level," said Ms O'Toole.

In the action, the genetic parents of twin girls born to a surrogate mother are seeking to have their children's birth certificates amended to name the genetic mother rather than her sister who gave birth to them.

Lawyers for the Attorney General said it was an inescapable conclusion that the birth mother is "of necessity" the mother for the purposes of Irish law because of the physical connection between a pregnant woman and her unborn.

Fatherhood does not involve gestation, Ms O'Toole who said that previously there had been no issue with the term "biological mother".

The State has argued that genetic connection alone is not given a high value.

Genetic connection without more is not a value to which huge significance will be attached in and of itself," said Ms O'Toole who added that "the laws of nature" means mothers and fathers are fundamentally different in law.

"The difference for mothers, of course, is they must bring the child through pregnancy and birth.

"Giving birth, being pregnant is what makes mothers fundamentally different to fathers," said Ms O'Toole.

Earlier today the Iona Institute intervened in the debate as it launched a paper "making the case against surrogacy".

The Iona Institute, which promotes marriage, religion and the defence of denominational schools, that the surrogacy case before the High Court shows why new reproductive techniques should not be used to divide or 'split' motherhood between two or more women.

"It creates an automatic ambiguity about who the mother of a child really is," said the Institute in a statement.

"Surrogacy is sometimes undertaken as an act of generosity, but is an emotional and legal minefield for all concerned, particularly for the child".