Fortis released this artist's rendering of a building complex the company is proposing in St. John's. (CBC)

Critics are speaking out against a proposal to build a new 15-storey office tower in St. John's.

If approved by city council, the $75-million dollar proposal by Fortis Properties Corporation would change the face of the capital's harbourfront.

"I was horrified. There is no design. These are two blocks," said Heritage advocate, Shane O'Dea, who has seen an artist's rendering of the proposed highrise.

Fortis wants to retrofit its existing building at the corner of Water and Prescott streets in St. John's and construct a new 15-storey building next to it.

The first four floors would contain retail space on Water Street and three hundred and eighty parking spots.

The office tower exceeds the city's height restrictions for downtown development, and will need special permission from city hall.

Deputy Mayor Shannie Duff is against the proposal.

"I find it shocking and it's very disappointing because I think Fortis which is a major, well-resourced company had an opportunity to do something really positive."

O'Dea fears it will have a powerful impact on future development in St. John's.

"The spin-off effect of other people coming back requesting further height allowances on their structures is going to mean a wall of glass and steel right along the harbourfront," said O'Dea.