European Parliament president Jerzy Buzek has promised a "zero tolerance" approach to corruption amongst MEPs.
Opening the mini-plenary session from Brussels on 23 March 2011, he raised the "cash for amendments" scandal uncovered in a British newspaper.
Two MEPs - Austrian Ernst Strasser and Slovene Zoran Thaler - have resigned, after being caught offering to table amendments in return for payments from a fake lobbyist firm.
A third MEP implicated in the scandal - Romanian Adrian Severin - has been expelled from his parliamentary group and now sits as independent, although there are calls for him to resign.
Jerzy Buzek said he would "stand guard of the honesty of the chamber", although Austrian independent MEP Hans-Peter Martin claimed there could be many more MEPs implicated.
Elsewhere during the opening of the session, President Buzek highlighted violence in Bahrain and Yemen, and said "governments turning guns on their own people lose all democratic legitimacy".
There was controversy over the appointment to parliament of former French interior minister Brice Hortifeux.
He was elected as an MEP in 2009 but decided not to take up his seat to concentrate on his domestic role, which he has since lost in a reshuffle by President Sarkozy.
Read Democracy Live's guide to how the plenary sessions work