The star said “great parts are being written” for actresses over 40 and that “times are changing”.
But the 43-year-old told the Times: “I’ve only just asked to be paid the same to do exactly the same work as someone else.
“In the past, it was always a case of take it, no questions asked, because if you don’t someone else will take it.
“You need a big profile to be able to stand up for yourself. It took people like Jennifer Lawrence saying it to move things forward.”
The Durrells star added: “It made her unpopular at the time but it’s started a hugely powerful movement.
“Generally, the statistics for women’s pay are still horrific compared with men’s, but it’s all moving in the right direction.”
Keeley is 11 years older than Richard Madden, the actor who played her lover in the TV hit Bodyguard.
But she told the newspaper: “The age gap was not ever mentioned. It’s not in the script, not discussed by anybody.”
Keeley has previously dismissed claims she went on a diet in preparation for her role in the hit BBC drama.
The actress, who plays a fictional Home Secretary in the series, shared a Mailonline article about herself, which claims she lost a stone by doing the alkaline diet.
In a tweet she said: “Um, no, I didn’t.”
She added in a hashtag that she didn’t know what an alkaline diet was.