A City of London skyscraper, nicknamed the Walkie Talkie, has won the annual Carbuncle Cup, awarded to a building judged to be the UK's worst.
Thomas Lane, who runs the awards, said the carbuncle "crashes into London's skyline like an unwelcome party guest".
A YMCA building and student halls in Cambridge were also in contention.
Other buildings vying for architecture's wooden spoon were Parliament House, Southampton City Gateway and Woodward Hall in north-west London.
Mr Lane, editor of Building Design magazine, said it was a challenge to find anyone with something positive to say about the Walkie Talkie, officially known as 20 Fenchurch Street, which was completed in April 2014.
"It bulges out towards the top in a cynical move to maximise the amount of high-value space at the upper levels, in defiance of the principle tall buildings should taper elegantly inwards or at least feature parallel sides," he said.
"The result is Londoners now have to suffer views of this bloated carbuncle."
During its construction, sunlight reflecting off the glass exterior melted parts of a Jaguar car.
It has also been reported that the tower, designed by Uruguayan architect Rafael Vinoly, creates a wind tunnel effect at its base.
Previous winners of the Carbuncle Cup include apartments above a Tesco store in Woolwich, south-east London, Liverpool's ferry terminal, student flats in north London, the renovation of the Cutty Sark and the Strata Tower in south London's Elephant and Castle.
To find a winner, readers of Building Design nominate their most hated buildings, which are then whittled down into a shortlist by a jury of architects and writers.