The Booker prize jury chair has bemoaned the quality of many entrants for the annual literary award, saying judges had often wondered “why we had been asked to read” some of the submitted novels.

Roddy Doyle, the first former Booker prizewinner to subsequently chair the jury, said he and the other four jurors had discarded all but 31 books from the original 153 to discuss before deciding which should be on their longlist.

He said many had not warranted discussion later, adding that he began to feel low when reading two bad books in a row because he had “signed up” to be a judge in order to read good books.

There are regularly more than 150 “literary fiction” titles in contention for the prize. New novels by all previously shortlisted authors are entered automatically, and some publishing houses are allowed several entries each depending on previous success.

The American writer Susan Choi is on the shortlist