The lawyer who acts for the author Harper Lee has spoken about the controversy surrounding a recently discovered sequel to To Kill a Mockingbird and the feelings of the author of the American classic about plans to publish it.

Tonja Carter said Lee (88) was "extremely hurt and humiliated" by reports that she had been being duped by people who wanted to publish the work, Go Set a Watchman, without her approval.

Ms Carter told the New York Times Lee was "a very strong, independent and wise woman who should be enjoying the discovery of her long lost novel. Instead she is having to defend her own credibility and decision-making."

Ms Carter said she found the manuscript of Go Set a Watchman late last summer and showed it to Lee, who said the book was the "parent" of To Kill a Mockingbird and said she presumed it had been long lost.

News of the discovery broke last week. Publisher HarperCollins said it planned to publish Go Set a Watchman later this year. Lee had not published another book after the staggering success of To Kill a Mockingbird, 55 years ago.

Joy, however, was accompanied with questions about whether Lee understood and approved of what was happening. Friends and neighbours in Monroeville, Alabama – the basis for Mockingbird's Maycomb and where Lee lives in an assisted-living facility – spoke of the reclusive author being adamant she never wanted to publish anything else.

There was also talk that the author may have been left vulnerable to unscrupulous business associates since the death of her sister Alice last year, at the age of 103. – (Guardian service)