The 160-metre tower, officially named 20 Fenchurch Street, was announced as the winner of this year's Carbuncle Cup award by organisers Building Design (BD) magazine.
The judging panel was chaired by BD editor Thomas Lane and included writer, broadcaster and historian Gillian Darley, architectural designer Eleanor Jolliffe – both columnists for BD – and Ike Ijeh, the magazine's architecture critic
Ijeh called the Walkie Talkie "a gratuitous glass gargoyle graffitied onto the skyline of London," while Jolliffe described it as a "Bond villain tower, as it could melt your car with a solar beam from space".
Completed earlier this year, the project received multiple nominations and was included on a shortlist of six, unveiled on 28 August.
The list also included the Woodward Hall development in North Acton, the "pastiche" Whittle Building at the University of Cambridge, the Waltham Forest YMCA building, Southampton's City Gateway project and the Parliament House tower in Lambeth.
The controversial Walkie Talkie gained its nickname for its distinctive shape, created by larger floor plates on the upper levels compared to those closer to the ground. Its top levels are taken up by the public Sky Garden, which helped the project win planning permission.
While still under construction, its concave glass facade concentrated a beam of sunlight onto nearby cars, melting parts of the bodywork and earning it the nickname Walkie Scorchie.
It hit the headlines again earlier this year after reports claimed that its curved facade is channelling gusts of wind strong enough to knock people over.
Uruguayan architect Viñoly admitted himself that they had "made a lot of mistakes" with the building.
The annual Carbuncle Cup award is named after part of a 1984 speech made by Prince Charles, who called a proposed extension to London's National Gallery a "monstrous carbuncle".
Last year's winner was the "oppressive" Woolwich Central development, while previous laureates have included a "prison-like" student housing block and Grimshaw architects' museum around the Cutty Sark ship – all in London.