Thomas R. Bradley, president of the Maryland-D.C. chapter of the AFL-CIO and the chief spokesman for the labor movement in Maryland, died today of an apparent heart attack.

Bradley, 55, suffered a heart attack on Oct. 11 but had returned home Monday.

This afternoon, he was stricken again and was taken to Franklin Park Hospital in Baltimore, where he died soon after arrival.

Bradley was known as an intense, emotional man who was devoted to the people he represented.

Typically, his final legislative meeting, three weeks ago, ended in a shouting match with Maryland Senate President Melvin A. Steinberg. They clashed over Steinberg's proposal for a special session of the legislature to continue an extended benefits program for the unemployed. Although Bradley supported the concept, he found untenable Steinberg's proposal that, in return for the extended benefits, labor agree to a one-week waiting period before laid-off workers could receive benefits.

As a result, Steinberg and Bradley yelled at each other, first behind closed doors, then in front of reporters, before Bradley stalked from the room.

"That was Tom Bradley's way though, he was an advocate," said Maryland Attorney General Stephen H. Sachs. "Tom truly represented what was best about the labor movement. He was a throwback, he really was a humanitarian voice for social justice."

Steinberg, vacationing in the Caribbean, sent a statement to his secretary: "I've known Tom Bradley for over 20 years. He was a dynamic and energetic person and he will be sorely missed in the labor movement. I will miss him. He was an advocate and I will miss our relationship."

Gov. Harry Hughes, who received the AFL-CIO's endorsement during his reelection campaign last year largely because of his friendship with Bradley, said, "Tom Bradley's death is a loss not only to the labor movement he served so well and honorably but also to the cause of good government, freedom and justice. As a recipient of his advice and counsel and as a friend, I will miss him."

"He was the right man in the right place at the right time for labor," said Speaker of the House of Delegates Benjamin L. Cardin. "He held the respect of everyone down here, whether they agreed with his positions or not."

Joslyn N. Williams, president of the AFL-CIO's Metropolitan Washington Council, said that "what stood out about Tom Bradley was his ability to bring people together, even people who disagreed vehemently on issues . . . It is a quality that few leaders have . . . and I think he was one of the preeminent labor leaders in the country."

Bradley was a machinist who rose through the ranks of the AFL-CIO to become its state president in 1979. He was a familiar figure in the hallways here as he bounced from one committee to another to work for and against bills involving labor. Last session, he played a key role in the passage of a compromise prevailing wage bill, a measure labor had been supporting for years.

Bradley will be succeeded, at least temporarily, by first vice president Henry Kollein.

"Tom was a hell of a leader and filling his shoes will be very difficult for us," said Ed Mohler, state financial director.