The European parliament is to begin its new five-year term in Strasbourg following elections last month.
One of the first tasks of the 736 MEPs will be to elect a new parliament president. Former Polish Prime Minister Jerzy Buzek is expected to be chosen.
But they will postpone for at least two months a vote on reappointing European Commission chief Jose Manuel Barroso.
The new parliament will include right-wing groups that made gains in June, including the British National Party.
Correspondents say it is not clear how British MEPs from the political mainstream will interact with their two colleagues from the BNP.
It is also not yet clear whether the BNP will be form a new bloc with other far-right MEPs - including those from Hungary's Jobbik, France's National Front, Belgium's Vlaams Belang, Bulgaria's Ataka, the Danish People's Party, and the Dutch Freedom Party - or be independent.
Strongest bloc
June's election produced a clear victory for centre-right parties across Europe.
Although the 25 British Conservative Party MEPs have left the European People's Party to form the European Conservatives and Reformists Group (ECR), the EPP remains the strongest bloc in parliament with 264 seats.
The centre-left Progressive Alliance of Socialists and Democrats in Europe (PASDE) is the second largest bloc with 183 MEPs, followed by the Alliance of Liberals and Democrats for Europe (ALDE) with 84.
One of the first tasks of the 736 MEPs will be to elect a new parliament president. Former Polish Prime Minister Jerzy Buzek is expected to be chosen.
But they will postpone for at least two months a vote on reappointing European Commission chief Jose Manuel Barroso.
The new parliament will include right-wing groups that made gains in June, including the British National Party.
Correspondents say it is not clear how British MEPs from the political mainstream will interact with their two colleagues from the BNP.
It is also not yet clear whether the BNP will be form a new bloc with other far-right MEPs - including those from Hungary's Jobbik, France's National Front, Belgium's Vlaams Belang, Bulgaria's Ataka, the Danish People's Party, and the Dutch Freedom Party - or be independent.
Strongest bloc
June's election produced a clear victory for centre-right parties across Europe.
Although the 25 British Conservative Party MEPs have left the European People's Party to form the European Conservatives and Reformists Group (ECR), the EPP remains the strongest bloc in parliament with 264 seats.
The centre-left Progressive Alliance of Socialists and Democrats in Europe (PASDE) is the second largest bloc with 183 MEPs, followed by the Alliance of Liberals and Democrats for Europe (ALDE) with 84.
NEW PARLIAMENT IN FIGURES
Half of MEPs were re-elected, half are new
Highest proportion of newly-elected MEPs is from Lithuania
Youngest MEP - Emilie Turunen (Danish), 25
Oldest MEP - Ciriaco De Mita (Italian), 81
Women MEPs - 35.3% (31.2% in old parliament)
Finland has most women MEPs (61.5%)
Malta has no women MEPs
Highest proportion of newly-elected MEPs is from Lithuania
Youngest MEP - Emilie Turunen (Danish), 25
Oldest MEP - Ciriaco De Mita (Italian), 81
Women MEPs - 35.3% (31.2% in old parliament)
Finland has most women MEPs (61.5%)
Malta has no women MEPs
See distribution of seats within the European Parliament
Quite how influential the ECR will be in the new parliament should become clear when the members and chairmen of the powerful committees are decided, says the BBC's Dominic Hughes in Strasbourg.
The EPP and PASDE are expected to share the presidency of the parliament over the next five years, with Mr Buzek, a former conservative Polish prime minster, likely to be the first to occupy the top job for two-and-a-half years.
Our correspondent says the president sets the tone of the parliament and can rule on points of order. The post holder also represents the assembly to heads of state and government.
Absent from the session, however, will be a vote on the reappointment of Mr Barroso as president of the European Commission, the EU's executive arm.
The former Portuguese PM has support of all 27 member states, but his centre-right allies in the assembly do not have a majority.
The Greens bloc, which increased its number of MEPs to 52, said in a statement on Monday that it did "not trust him to wholeheartedly implement the policies that Europe urgently needs" as a result of his handling of the economic crisis in recent months.
The chairman of the PASDE, Martin Schulz, meanwhile said EU nations had made a mistake by trying to force a vote well before Mr Barroso's term ended in October.
"They wanted to rush this through, and we have prevented that. We will see and hear in September what Mr Barroso has to say and discuss with him," he said. "What I have seen over the past weeks does not make me hopeful." The Swedish presidency, which took over from the Czech Republic on 1 July, will lay out its priorities for the next six months on Tuesday.
The EPP and PASDE are expected to share the presidency of the parliament over the next five years, with Mr Buzek, a former conservative Polish prime minster, likely to be the first to occupy the top job for two-and-a-half years.
Our correspondent says the president sets the tone of the parliament and can rule on points of order. The post holder also represents the assembly to heads of state and government.
Absent from the session, however, will be a vote on the reappointment of Mr Barroso as president of the European Commission, the EU's executive arm.
The former Portuguese PM has support of all 27 member states, but his centre-right allies in the assembly do not have a majority.
The Greens bloc, which increased its number of MEPs to 52, said in a statement on Monday that it did "not trust him to wholeheartedly implement the policies that Europe urgently needs" as a result of his handling of the economic crisis in recent months.
The chairman of the PASDE, Martin Schulz, meanwhile said EU nations had made a mistake by trying to force a vote well before Mr Barroso's term ended in October.
"They wanted to rush this through, and we have prevented that. We will see and hear in September what Mr Barroso has to say and discuss with him," he said. "What I have seen over the past weeks does not make me hopeful." The Swedish presidency, which took over from the Czech Republic on 1 July, will lay out its priorities for the next six months on Tuesday.
