Antonio Tajani | Photo European Parliament audiovisual
In a speech on Tuesday to mark the 60th anniversary of the treaty of Rome, he insisted that no member state alone could hope to solve the issues facing Europe.
These, he told a packed chamber in Brussels, include tackling migratory flows, defending economic interests and halting global warming.
"These cannot be solved by a weakening of the EU," said the Italian MEP.
With far-right party Front National continuing to poll well ahead of next month's French presidential election, he also cautioned against populist parties.
The EPP group member said, "I would urge member states to avoid the temptation to venture into nationalism."
Speaking in the same debate, the renowned Austrian writer Robert Menasse warned that the EU was "teetering on the brink."
He told MEPs, "When it comes to the EU's future we are at the 11th hour and do not have much more time."
Without naming names, he blamed Europe's "political elite" for many of the ills that have befallen the EU, saying, "They clearly have forgotten, or maybe never knew, what the whole EU idea is about."
The academic, who was given a standing ovation, also cautioned against Scotland being "betrayed" in the Brexit talks.
He said, "The Scots want to stay in the EU and this should be respected. The negotiators should not give in to the nationalists in London."
Later on Tuesday, Parliament will hold a 'Citizens' Parliament', bringing together people from all over the EU to discuss the future of the EU in the plenary chamber.
As part of the ongoing celebrations to mark the 60th anniversary, on Friday, there will be a special meeting of the parliamentary Conference of Presidents (its President and political groups' leaders) and the bureau (Vice-Presidents and Quaestors) in Norcia, Italy, in the region hit by the recent earthquakes, where they will meet Italy's Prime Minister Paolo Gentiloni.
Tajani and the presidents of the other two EU institutions will meet Pope Francis later in Rome.
On Saturday, Tajani will deliver a speech at the 60th anniversary celebration, sign the Rome declaration on behalf of Parliament and take part in a joint press conference with the leaders of the other EU institutions.