The Prince of Wales last week took a swipe at the view from Southwark Cathedral during a visit to the new Millennium development.
The Prince was talking with Benjamin Finn, a stained glass artist, about his work, when he spotted the office block, which is covered in scaffolding.
After commenting, "Oh dear, what's that?" he told the artist he should block the view by using stained glass to cover the whole of the new cathedral window.
The Dean of Southwark, the Very Rev Colin Slee, said afterwards: "I told him that it [the office block] was going to be a glass cube. He doen't like that."
But Slee added, "Sometimes a glass cube near an ancient building can set it off, so I'm not opposed to all modern buildings."
The Prince passed on his views to some of the crowd of people who had been waiting outside the courtyard to catch a glimpse of him.
Jane Berntsen, marketing and communications manager of private bank Ansbacher, which owns and is in charge of renovating the building, defended the five-storey block.
"It's an important part of the development and regeneration that is very positive for the area."