By Alix Kroeger
BBC News, Brussels
For the first time in more than a decade, the far-right has assembled a bloc in the European Parliament.
Bulgarian and Romanian MEPs bring the total in parliament to 785
The arrival of MEPs from European newcomers Bulgaria and Romania in parliament has given the far-right enough seats to form an alliance.
The bloc's leader Bruno Gollnisch said it would base itself on Christian values and on human rights.
But other groups in the parliament are concerned. Some have proposed measures to shut the far-right out of power.
The leader of the centre-left Socialist group, Martin Schulz, has suggested a "cordon sanitaire" to keep them out of official positions.
Speaking outside the parliament, Mr Gollnisch said he was beginning to agree with the former Italian Prime Minister Silvio Berlusconi, who had compared Mr Schulz to a Nazi concentration camp guard.
Mr Schulz wants the parliament to investigate the legality of the group, after one of its members, Italian MEP Alessandra Mussolini said in an interview that it was a technical, not a political group.
But Mr Gollnisch said the group had a very clear political programme - an assertion which other MEPs will be watching closely in the months to come.
The parliament in Strasbourg formally welcomed 35 Romanian and 18 Bulgarian MEPs on Monday - bring its total to 785 - for the first plenary session since they joined the EU on 1 January.
The new MEPs have been appointed by their national parliaments and will keep their seats until European elections in the two countries later in the year.
Translation booths have already been installed for the Romanian and Bulgarian languages, along with Irish, which is now the 23rd official language of the EU.
The accession of Romania and Bulgaria has allowed far-right parties from across the EU to meet the criteria to sit as a recognised political group and get funding - parties which mostly opposed EU membership for Romania and Bulgaria in the first place.