The late Philip Johnson once described architects as "high-class whores" - and he was one of the most successful of them, writes Frank McDonald, Environment Editor

All professions have their charlatans, and architecture is no exception. Philip Johnson was surely one of its greatest, having championed the cause of modernism in his youth and produced a few of its better buildings, he abandoned it all for post-modernist flights of fancy when that became the thing to do.

"Values can change . . . we can do anything," he said in his acceptance speech in 1979 when he was awarded the first "Pritzker Prize for Architecture". Then aged 73, he was being honoured for "50 years of imagination and vitality embodied in a myriad of museums, theatres, libraries, houses, gardens and corporate structures".

It is for "corporate structures" such as the mock-gothic Pennzoil Place in Houston, Texas, and the pretentious AT&T Building on Madison Avenue, in New York, that he is chiefly known.

"The people with money to build today are corporations - they are our popes and Medicis," Johnson said. And he went for the money.

"I am a whore and I am paid very well for high-rise buildings," he openly admitted. He said later that his choice of words was "unfortunate"; all he meant to suggest by his colourful phrase was that architects are "for sale" to clients and must compromise accordingly. "An unprofitable skyscraper simply would not be built."

As for his flirtation with fascism in the 1930s, Johnson said decades later that he had "no excuse for such utter, unbelievable stupidity" and he was just "a damned fool". He had heard Hitler speak at one of the Nuremberg rallies and, according to Andrew Saint, he was "titillated by the aesthetics and sexuality of Nazism".

But Johnson went further. Along with a firebrand Irish-American priest, Father Charles Coughlin, he founded an American version of the Nazi party and even designed its emblem, described by Saint as a "flying wedge". He also accompanied German troops in Poland and said of the burning of Warsaw that it was a "stirring spectacle".

While in his mid-20s, he had travelled extensively in Germany as an emissary of New York's Museum of Modern Art (MoMA), seeking out innovative architecture. That produced a major exhibition, "The International Style" in 1932, which is credited with having a powerful role in popularising modern architecture in the US.

It was also the vehicle that gave Mies van der Rohe a transatlantic toe-hold. At that stage, Johnson was a huge fan of Mies's clean lines and the idea of form following function - one of the keystones of the modernist aesthetic. The Glass House he built in 1949, a "cube in the woods" near New Canaan, Connecticut, owes a lot to Mies.

Ironically, the place where Johnson lived and died was finished before Mies's Farnsworth House, in Plano, Illinois, which occupies a higher plane in the annals of architecture. He later collaborated with Mies on the iconic Seagram Building, completed in 1958, though his work was confined to the interiors, notably the Four Seasons restaurant.

Johnson, a rich lawyer's son from Cleveland, Ohio, first studied philosophy at Harvard and only later turned to architecture. With his Chicago-born partner, John Burgee, he produced such diverse work as a major extension to Boston Public Library, Pennzoil Place in Houston and the Garden Grove Crystal Cathedral in Los Angeles.

He had once declared that his ambition was "to build the greatest room in the world". The Crystal Cathedral, an over-sized greenhouse commissioned by television evangelist Robert H Schuller, is bigger than Notre Dame in Paris - there's seating for nearly 3,000 worshippers under its 10,900 panes of dazzling reflective glass.

But it was the AT&T Building, which he described as "the job of my life", that really made its mark, putting him on the cover of Time magazine.

Designed in 1978 and completed in 1984, its Chippendale top, pink granite cladding and monumental entrance rising to a height of 90 feet turned him into a high priest of post-modernism.

Corporate America bowed down before him and the result - as Robin Middleton, professor of art history at Columbia University, complained - was a plethora of post-modern office towers "imbued with the dull complacency of wealth" in cities such as Houston, Pittsburgh, San Francisco and, worst of all, New York's garish "Lipstick Building".

In his Pritzker acceptance speech, Johnson described architecture as "the most difficult of all the arts. How often I have envied my colleagues who write, paint or compose music. They live where they like, they work when they want, no recalcitrant materials, no leaky roofs, no stopped-up sewers. They tear up their mistakes."

Sadly, many Americans must live with his. Way back in 1961, delivering a lecture to the Architectural Association in London, Johnson advised his fellow architects that they should "choose from history whatever forms, shapes or directions you want . . . using them as you please." Even then, he was on his way to becoming a charlatan.

Cesar Pelli, architect of London's Canary Wharf towers, said recently of the AT&T Building (now Sony) that its post-modernist excess "hit it right on the head at that time. That building's name was not made by Philip, it was made by the media. And this was another way he influenced architecture. Philip loved the media."

Johnson was an architectural impresario. As Aaron Betsky noted: "He did not invent. He did not have a tortured process of arriving at just the right form. He just gave a twist and flip, flourished a column or a grid, and voilà, the rabbit of architecture appeared out of the hat of the elegant Park Avenue gentleman."

Towards the end of his life, he went public with the fact that he was gay - something everyone who knew him knew already. Though his homosexuality had tortured him in his youth, his early trips to Berlin released him from his mid-western inhibitions and, as he said much later, he learned German by "the horizontal method".

One of the best stories involving Johnson is told by an eminent Irish architect. He had a difficult client who was always demanding design changes and said he was getting too old for that sort of stuff. "What are you talking about?", the well-known property developer retorted. "Sure Philip Johnson is 95 and he has a new boyfriend."

Described by some as "the Andy Warhol of architecture", Johnson once told Daniel Libeskind that what defined it was "a feeling in the stomach" from the sensation of seeing a building with a real "wow factor". In his will, he left the Glass House in New Canaan - perhaps his only real masterpiece - to the US National Trust.

Philip Johnson, born 1906, died January 25th, 2005