Three-month TSX trading in Magna A shares.

Magna International Inc. will slash 400 jobs at its plant in St. Thomas, Ont., because of falling demand for pickup trucks, the company said Wednesday.

The plant, which has 1,600 employees, makes frames for General Motors pickups.

"This is the first permanent layoff situation since the plant's inception, reflecting a considerable downturn in consumer demand for full-size trucks and a corresponding reduction in customer production volumes," Magna said.

The Magna layoff is set for Sept. 8.

GM pickup sales have fallen sharply this year with higher gas prices. The company announced recently that it is set to close its pickup assembly plant in Oshawa, Ont., in 2009.

That has led to a confrontation with the Canadian Auto Workers union, which says the planned closing violates its contract with GM.

Magna reported first-quarter profit of $207 million US ($1.78 a diluted share), compared with $218 million ($1.96) in 2007. Revenue was $6.62 billion, compared with $6.42 billion.

Magna stock slid $1.02 Cdn to end at $70.52 on the TSX. The 52-week range is $67.51 to $102.

With files from the Canadian Press