The Kimmel Center sued Rafael Viê±oly Architects late last year, charging that flaws and delays in the construction of the four-year-old complex cost it millions. The Kimmel Center cost $180 million to build, about $23 million more than the amount budgeted for construction. The lawsuit alleges that "most, if not all, of the cost overruns" were the fault of Viê±oly Architects.

In his letter, which was sent to the center's chairman and board member and forwarded to the Inquirer, Viê±oly blamed the overruns on the center's managers, who indulged in "late decisions and gilded tastes."

"The Kimmel expanded the size of the project and increased the budget after the architect was commissioned," he added. "This escalation was the result of the failure of [the Kimmel Center] to make timely and consistent programmatic and budgetary decisions."

The Kimmel Center's lawyer told the Inquirer that the letter was "false and defamatory," but declined to comment further because the lawsuit is still in litigation.