Chanel's creative director accused Streep of rejecting one of his dresses because she found a different designer who was willing to pay her.
He has since said he "misunderstood" - but that has not calmed Streep's ire.
"I do not take this lightly, and Mr Lagerfeld's generic 'statement' of regret for this 'controversy' was not an apology," she said.
She also criticised fashion website WWD, which originally reported his quotes.
"He lied, they printed the lie, and I am still waiting," she said in a statement.
The dispute began when WWD published an interview in which Lagerfeld said he had started work on a dress for Streep to wear to Sunday's Academy Awards.
But he claimed he was then told by one of the actress's representatives: "Don't continue the dress. We found somebody who will pay us."
Referring to Streep, he said: "A genius actress, but cheapness also, no?"
The designer later issued a statement admitting he had "misunderstood that Ms Streep may have chosen another designer due to remuneration" and said he regretted the controversy.
However, Streep, who has her 20th Oscar nomination this year for Florence Foster Jenkins, hit back.
She said Lagerfeld "defamed me, my stylist and the illustrious designer whose dress I chose to wear, in an important industry publication".
Her statement added: "The story was picked up globally, and continues, globally, to overwhelm my appearance at the Oscars, on the occasion of my record-breaking 20th nomination, and to eclipse this honour in the eyes of the media, my colleagues and the audience."
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Meryl Streep's choice of dress for the Oscars has sparked a bitter row between the star and designer Karl Lagerfeld.