A hearing is taking place in the European Parliament in Brussels on an initiative to oblige the EU to ban funding for activities that "presuppose the destruction of human embryos".
The 'One of Us' campaign wants the European Commission to propose a ban to no longer fund research involving human embryos.
The initiative has the support of a number of European faiths including the Catholic Church and has collected almost 1.8 million signatures.
However, opponents of the move, including the Irish Stem Cell Foundation, say it would be a major step backwards for research across regenerative medicine, reproductive health and genetic disease.
One of the innovations of the Lisbon Treaty was the Citizens' Initiative, whereby citizens can request the European Commission to adopt, or drop, legislation on a given subject, if they gather over one million signatures from at least 20 member states.
One such petition is 'One of Us', which calls on the commission not to provide any funding for stem cell research or any research which relies on the destruction of human embryos.
The campaign, spear-headed by a number of Italian and Spanish MEPs, but supported by anti-abortion groups in Ireland and elsewhere, also wants to block the funding of organisations that, they say, encourage or promote abortion.
The campaign has raised over 1.7m signatures and so meets the criterion.
A number of relevant committees in the European Parliament will assess the petition before asking the commission to give its response.
However, a number of women's health organisations, as well as scientific research bodies, have strongly condemned the petition.
They say it is the work of ultra-conservative religious groups, and have warned that such a ban would seriously hamper research into degenerative diseases such as Parkinson's and Motor Neuron disease.