Former Polish President Lech Walesa has hit out at EU labour policies while guest of honour in Strasbourg.
Lech Walesa described some policies as communism
Mr Walesa compared some EU rules concerning workers from new member states as "communism".
The founder of Poland's Solidarity trade union was in France for the first European Parliament session since 10 new member states joined on 1 May.
Flags were presented and raised next to those of the 15 older members at a ceremony before the session.
Expansion means MEPs are joined by 162 representatives from the new members, who have been observers until now.
Mr Walesa has described the EU's expansion as "my lifelong dream... come true".
But on Monday, he compared the labour policies to those of the communist regime he had fought against.
Mr Walesa highlighted the transition period of up to seven years, demanded by Germany and Austria, during which workers from the new EU member states will not be able to work in the old 15 countries.
"This is communism," he told reporters.
"How can you come up with such an idea? It's really strange that you don't want to take advantage of better skilled and cheaper workers.
"The present economic solutions, democratic solutions are not from this epoch. They date back to the epoch of divisions. They can't stand the pressure of the 21st Century."
The newcomers to the EU are: Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia.