A new European treaty will not be concluded before Ireland takes the presidency of the European Union, the Forum on Europe has been told.
Ms Kirsty Hughes, an expert on European affairs, told the forum that significant issues remained to be resolved on the next treaty.
Despite a push by the Italian presidency for negotiations to be concluded for agreement by the end of December, Ms Hughes said divisions between member states on some major issues remained.
This was because the Italians were anxious that the new treaty be called the Treaty of Rome, she said.
"I think that negotiations are highly likely to go into next year. And I think the haste of the Italians isn't necessarily going to help negotiations."
She made her comments at the autumn sitting of the forum at Dublin Castle, which was discussing the draft constitution for Europe. The draft was agreed by the specially formed European Convention in July, involving all member states.
The inter-governmental conference (ICG) will begin deliberations on the draft next month, with a view to reaching agreement at the next EU Heads of State meeting at the end of this year.
However Ms Hughes, a senior research fellow at the Centre for European Policy Studies in Brussels, said significant issues remained to be resolved.
Chief among them were reforms to the institutions of the European Union, the Commission, Council and Parliament, and striking the balance of powers between them.
Ms Hughes believed this aspect of the convention agreement was rushed, resulting in "a messy" deal.
Issues as yet unresolved surrounded the role and powers of the new Council of Europe President and the new European Foreign Affairs minister, she said.
However further negotiations at ICG level, she believes could result in things "being made worse rather than better", she warned.
She welcomed the new proposals for the introduction of two-thirds-majority qualified voting for some Council of Europe decisions as "simple, clear and easy to understand".
Mr Gijs de Vries, the Dutch representative at the Convention, also told the forum that the finely balanced relationship between large and small countries had not been upset by the new constitution's proposals.
Mr De Vries, a former leader of the National and Democratic Group, at the European Parliament, said he believed a good "balance" had been achieved in the convention, despite various unresolved issues and concerns.
"I think the convention has been a success in strengthening democratic checks and balances, transparency and human rights protection," he said.