Construction work has started on the first phase of the Laurel Centre's expansion - a $52 million project that will add two major department stores and create a combined retail center with 1.2 million square feet.

The first phase, to cost 30 million, will link the old Laurel shopping center and its Hecht's store with an existing Montgomery Ward unit now about a block away.

In between will be located an 83,000-square-foot J.C. Penney unit, one of six new area Penney stores under construction or planned between 1979 and 1982. The Penney at Laurel and a two-level, 265,000-square-foot enclosed mall between Hecht's and Ward is scheduled to open in the fall of 1979 as one of the largest retail complexes in Prince Geoge's County.

When completed, Laurel centre will have about 150 stores withe projected annual about 150 stores with projected annual sales of some $100 million.

A second phase of the expansion at Laurel will include a fourth department store, with 120,000 square feet. Retail soures said Woodward & Lothrop is among companies interested in the Laurel location.

Joseph Batleman and Joseph Mersel, who are working on leasing for the expanded mall, said a focus inside the center will be a restaurant plaza with food from many nations and ethnic backgrounds surrounding a seating area.

The 19-year-old Laurel shopping center currently produces about $50 million in annual sales from 510,000 square feet of retail space. Shopco Co. of New York is developing the mall expansion.