"I won't go to Lille because I don't want to become ... an accomplice to the assassination of the National Front that will be underway there", he told RTL radio.
"Let them call you racist", he told the crowd.
His European tour centered on last weekend's Italian election, which Bannon called "an earthquake" after populist and anti-immigration parties outperformed traditional parties.
"Welcome to Steve Bannon who will address the National Front tomorrow at our congress and will meet Marine Le Pen".
Le Pen came to Lille vowing to ditch the tainted FN brand, seen as a key hurdle to winning power, in favour of an as yet unannounced new name. But the pair had a bitter public falling out and Bannon was sacked by the White House last August, though he continued to speak with Trump and tried to promote the president's agenda.
She also defended her far-right party's stance against immigration and in defence of French culture and security.
All eyes instantly turned to her glamorous niece, 28-year-old former MP Marion Marechal-Le Pen.
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Bannon said he agreed with Le Pen's expressed belief that "it is not about left versus right".
Bannon has publicly praised Marechal-Le Pen in the past, and she galvanized the crowd at a recent convention of US conservatives. A new leadership structure and new bylaws are also being unveiled at the two-day congress.
Marine Le Pen is running unopposed for a third term and her address Sunday will see her try to turn a page on the anti-Semitic, openly racist party of her former paratrooper father.
Jean-Marie Le Pen said that in losing heavily to Macron his daughter had "not been equal to the challenge" - a sentiment echoed by many FN members.
Le Pen, the only candidate for National Front president, says the changes amount to a "cultural revolution" so the reshaped party can "implant itself, create alliances and govern".
An election next year for members of the European Union's lawmaking arm will be the National Front's first chance to test its rebranding strategy.
"She is not simply a rising star on the right in France".
However, Le Pen's credibility is among the potential obstacles to a possible far-right comeback: An annual poll published this week by the Kantar-Sofres-One Point firm showed Le Pen scoring lower on numerous questions.
The weekend congress is expected to erase one persistent problem for Le Pen - her unpredictable, bombastic father - by eliminating his title of honorary president-for-life from party statutes.