Fianna Fáil Senator Jim Walsh has resigned from Fianna Fáil over his opposition to the Children and Family Relationships Bill.

The Bill extends the definition of family and its provisions also include the extension of guardianship and adoption rights to new categories, including same sex couples. It also updates the law to bring clarity to the status of children born by donor-assisted methods, and of their parents.

Mr Walsh, from Wexford, is understood to be opposed to 36 sections of the Bill and has tabled an amendment asserting that IVF methods should be primarily for male and female married couples.

According to sources, he will also argue in the Upper House for the Bill to be amended to allow a hierarchy of parenting arrangements when the best interest of the child is being considered. A family where there is a father and mother should get priority, said a source familiar with Mr Walsh’s views.

If a vote was forced and Senator Walsh opposed the Bill, he would have been expelled from the party.