ooops pressed submit there by mistake. I believe that there is nothing to stop you having one drawn up but that they are not really recognised in the way that they are in America. However if one was drawn up there is certainly no harm in doing it I suppose. If you are concerned about a house purchase then you can always choose to own the property as tenants in common with your ownership clearly defined as a certain percentage.
Pre-nup agreements are not vaild in this country; they are deemed to be prejudicial to marriage, unless they form part of a reconciliation agreement. The rationale behind it is that one should not enter to into a 'contract' (Marriage) with a view to future destruction of that contract. The authority for that is
Macmahon v Macmahon [1913] 1 IR 428