PAWTUCKET — The General Assembly’s decision to close the state’s historic tax credits to new development projects has caused the prospective developer of a key downtown building to cancel his plans.

Lawrence J. Platt, who had been counting on using the lucrative 30-percent tax credit to provide part of the financing for the rehabilitation of the Old Colony Bank building, let city officials know he was dropping the project after the House Finance Committee voted to block developments that hadn’t applied for the tax credits as of the end of last year

“He was deeply disappointed,” City Planning Department Director Michael D. Cassidy said of Platt, after announcing the decision at yesterday’s Pawtucket Redevelopment Agency meeting.

“The state’s elimination of historic tax credits for any project going forward just killed this project,” Cassidy said.

Platt didn’t immediately return a call seeking comment. Cassidy said the Providence-based developer had been planning to spend up to $3 million to convert the Old Colony Bank building into stores and offices, combining state and federal historic tax credits to raise part of the money.

Now that the state credits are no longer available, Cassidy said, “the numbers don’t work.”

It was the second time in three years that plans have fallen through for the Old Colony Bank building, a three-story ruin at 347 Main St. that the PRA acquired from China Inn restaurant owner Louis C. Yip four years ago.

In 2005, the reluctance of lenders to finance a project in downtown Pawtucket caused Federal Hill chef Walter Potenza to kill a proposal to turn the derelict bank building into a cafe and cooking school, as he planned.

Cassidy said he was undaunted by the latest setback and would eventually seek bids from other developers interested in rehabilitating the Old Colony building.

In the meantime, he obtained permission from the PRA to spend an unspecified sum on a cleanup of the building, which he said has been unoccupied for 12 to 15 years.

The cleanup won’t be extensive, Cassidy said. It will just involve removing the rugs that have gotten wet and moldy and the bird droppings that have accumulated inside since the bank closed.

The building is one of two properties in downtown Pawtucket that the city is trying to sell to a developer.

The other is the Edward J. Creamer building on Park Place, which the School Department abandoned when it moved its offices to 286 Main St. in 2006.

Last October, developer Everett A. Amaral, of Amaral Revite, offered to buy the Creamer building for $525,000 and convert it to offices.

After the state budget crisis caused Governor Carcieri and the General Assembly to consider trimming or even eliminating the historic tax credit program, however, Amaral told the City Council Property Committee that a tax treaty might be necessary to make the project work.

Cassidy said yesterday he hopes Amaral will go through with the project, even though no decision has been made on the tax treaty.

The roof leaks and many of the windows are broken in the Old Colony Bank building, Cassidy said. The Creamer building is in much better shape.

It has remained heated and sealed from bad weather since the School Department vacated it, Cassidy said, making it a much easier building to redevelop.

Amaral didn’t immediately return calls yesterday.

jcastell@projo.com