Rachel Johnson is the sister of London Mayor Boris Johnson
Author Rachel Johnson has been named as the winner of this year's Bad Sex In Fiction Award for a passage in her novel Shire Hell.
The winning section by Johnson, the sister of London Mayor Boris Johnson, includes the phrase "and a strange animal noise escapes me".
Tony Blair's ex-spokesman Alastair Campbell was among those shortlisted.
The award is given to the passage considered to be the most redundant in an otherwise excellent novel.
The awards, now in their 15th year, were announced at a ceremony in central London.
Johnson said: "I always wanted to win a literary award and to bag this coveted prize - a prize that has been won by admired giants such as Norman Mailer, Sebastian Faulks and Tom Wolfe - is, for me at least, a tremendous honour."
The prize, awarded by Literary Review magazine, was presented by actor Dominic West, star of US TV series The Wire.
Johnson's winning passage includes the following lines: "I find myself gripping his ears and tugging at the locks curling over them, beside myself, and a strange animal noise escapes from me as the mounting, Wagnerian crescendo overtakes me.
"I really do hope at this point that all the Spodders are, as requested, attending the meeting about slug clearance..."
John Updike's nod for his novel The Widows of Eastwick was his fourth consecutive nomination, earning him a lifetime achievement award.
The judges said in a statement that 76-year-old Updike had kept them "entertained for many years".
The other shortlisted books were The Gate of Air by James Buchan, All in the Mind by Alastair Campbell, To Love, Honour and Betray by Kathy Lette, Sashenka by Simon Montefiore, Attachment by Isabel Fonseca and The Reserve by Russell Banks.