Complex sentence: A spokesperson for the Prime Minister said that they did not "need to dignify the book by offering any comment", while friends reported him saying that the claim was "utter nonsense".
Split into simpler sentences: A spokesperson for the Prime Minister said that they did not "need to dignify the book by offering any comment". Downing Street sources responded by saying that Cameron would not dignify the allegations with a response, while friends reported him saying that the claim was "utter nonsense".