The Mail on Sunday reported that Lucilla Andrews had been planning to draw attention to the similarities between her autobiography ''No Time For Romance'' and sections of ''Atonement'' at an awards ceremony.
But the elderly writer fell ill and died last month aged 86.
Her former agent Vanessa Holt said that Andrews, who made a living from so-called ''hospital romances'', had been aware of the parallels between her autobiography and ''Atonement'' about a year before she died, after a student drew attention to them.
But Holt denied Andrews had been planning to make a public swipe at McEwan, one of the country's most revered authors.
''She may have taken a different view if she had been younger, but she was elderly when she found out,'' Holt told Reuters.
When asked what she thought of McEwan's rebuttal, printed on the front page of Monday's Guardian newspaper, Holt replied: ''I think I remain of the opinion that it was discourteous from one writer to another not to seek her approval.'' She added that the matter was unlikely to go any further.
The claim is the latest plagiarism controversy to hit the literary world. U.S. author Dan Brown appeared in court in London in February and March to deny accusations he copied wholesale to write his bestseller ''The Da Vinci Code''.
Brown won the high-profile case against two historians, although they have said they would appeal against the verdict.
McEwan, 58, said Andrews was a source of ''inspiration'' for his novel and its characters.
''An inspiration, yes. Did I copy from another author? No,'' he said on his Web site.
While researching ''Atonement'', his 2001 work shortlisted for the Booker prize for fiction, he came across ''No Time For Romance'' in an Oxford library and drew on its descriptions of life in a London hospital during World War Two.
''As with the Dunkirk section, I drew on the scenes she described,'' he wrote in his rebuttal.
''For certain long-outdated medical practices, she was my sole source and I have always been grateful to her.'' He added that he acknowledged his debt to Andrews in the author's note at the end of ''Atonement'' and spoke about her in numerous interviews.
''My one regret is not meeting her,'' he continued. ''But if people are now talking about Lucilla Andrews, I am glad.'' As with ''The Da Vinci Code'', ''Atonement'' is being adapted into a Hollywood movie, starring Keira Knightley. It is due for release in August and September 2007.
REUTERS SP PM1155