The Eurythmics star, 62, made the remarks as she attended an event in the capital ahead of International Women’s Day on Wednesday.
She was hosting the rally on Sunday afternoon with Mayor of London Sadiq Khan, human rights activist Bianca Jagger and the great-great granddaughter of suffragette leader Emmeline Pankhurst Dr Helen Pankhurst.
Singers Emeli Sande, Natasha Beddingfield and Kate Nash were also among the thousands of activists who turned out for the demo, which ended in a march over Tower Bridge.
Asked about comments made by Mr Trump in a 2005 leaked video in which he bragged about grabbing women "by the p****", Lennox said: "In a weird kind of way that kind of event that happened actually catalysed the issue for a lot of girls and women in a particular way that became very strong.
"All of a sudden there were a lot of people putting on pink p**** hats and saying no.
"It actually became very real for them, because when someone says 'It's just locker room talk', actually don't we think it's time that we should address that particularly if they're the leading representative of one of the biggest most influential countries in the world?
"So that made women very angry, that made the issue very clear for them.
"But actually what we're saying is that the issue is huge, looking at the developing world, that is just the tip of the iceberg.
"So there's so much more to address. We've been banging this drum for a long, long time. I welcome anybody that comes here, men and women.
"So in a funny way, the Donald Trump statement is almost helpful as a catalyst."
The CARE International rally and #March4Women event was organised to help shine a light on the inequality faced by women and girls around the world.
The group heard speeches from the organisers at a rally outside City Hall before marching along Tower Bridge holding banners aloft with the #March4Women slogan.
The famous London landmark was closed to traffic for the event.
The mayor shared photos from the event on Twitter and wrote: “Incredible atmosphere at #March4Women - thousands of Londoners standing in solidarity with women across the world. #InternationalWomensDay"
Many people taking part in the event also took to social media to share their images.
Speaking at the same event, Jagger, 71, said she had been “shocked and revolted” at Prime Minister Theresa May for inviting the president to Britain at a state visit.
"I'm deeply disappointed, not only disappointed in her as a politician, but I'm disappointed in her as a woman,” she said.
"To think that a woman was not ashamed to go to America to hold hands with a man who has bragged about sexually assaulting women, and who doesn't care that on that same day there was a Muslim ban and a ban against people because of their race, and a man who wants to build a wall with Mexico, and a man who says that the press is the enemy of the people.
"How can I not be disappointed? I'm shocked and revolted by her inviting Donald Trump."