Publisher Penguin Random House has dismissed claims that Lara Prescott, a debut novelist who received a $2m (£1.6m) advance for her novel about the publication of Boris Pasternak’s Doctor Zhivago, infringed the copyright of Pasternak’s great-niece Anna Pasternak as “simply without any merit”.

Published in September, Prescott’s The Secrets We Kept tells of how the CIA planned to use Doctor Zhivago as a propaganda tool during the cold war. But Anna Pasternak revealed in the Sunday Times that she had sent a legal letter to Prescott, claiming that the novel features “an astonishing number of substantial elements” copied from Pasternak’s 2016 biography Lara, which is about Olga Ivinskaya, Pasternak’s lover, muse and inspiration for his character Lara.

The letter sees Anna Pasternak claim that similarities “exceed the mere inspiration a novelist may legitimately draw from a work of non-fiction”. She is seeking damages or compensation for the alleged infringement of copyright.

An event with both authors at the forthcoming Cheltenham Literature festival – sponsored by the Sunday Times – has now been cancelled due to “unforeseen circumstances”.

On Tuesday, Penguin Random House said that it and Prescott considered Anna Pasternak’s claim to be unfounded.

“If proceedings are in fact issued, they will be robustly defended,” said the publisher. “Anna Pasternak’s claims are simply without any merit, and it is disappointing that she has chosen to litigate in the press rather than wait for the response to her letter of complaint within the timeline requested by her own lawyers.”

Penguin Random House pointed out that the story of Olga Ivinskaya has been the subject of multiple books before Anna Pasternak’s, including Ivinskaya’s 1978 autobiography, a book by her daughter Irina Emelyanova, and Peter Finn and Petra Couvee’s 2014 book The Zhivago Affair.

“The subject matter of both books is one of historical record and has been covered by other books in the past,” said the publisher.

When it was published in 2016, Lara was billed as: “The untold love story that inspired Doctor Zhivago”. A New York Times review said that “the ‘untold’ in the subtitle simply isn’t true” because “the story of Pasternak’s affair with Olga has been told repeatedly”. It concluded: “Pasternak fans and incurable romantics will be better off sticking to Doctor Zhivago, or searching out the earlier memoirs that serve as this new book’s central sources.”