Maryland Gov. Harry Hughes, at his first press conference in three weeks, said today he wants to spend about $12 million during fiscal 1985 on the first part of his extensive Chesapeake Bay cleanup program. He declined, however, to be specific on how that money would be spent.

The governor continued to be evasive on the question of an income tax increase, something legislative leaders and Hughes staffers have said is probably unavoidable, barring major changes in the revenue picture.

Hughes said he would wait until early December before making a decision on whether to seek a tax increase. Asked if he would seek a tax increase if not seeking one would mean giving up the bay program, Hughes said, "Yes, I would seek a tax increase."

He said he would do the same thing if the increase is needed to provide money for the new education funding formula to be presented next year and to provide state employes with a raise. But the governor said he still was not certain that step would be necessary.

Hughes also said there had been suggestions that the Bethesda-based Martin Marietta Corp. might be interested in taking over the airplane manufacturing plant in Hagerstown being abandoned by Fairchild Inc.

Fairchild is closing the plant at the end of the year, putting more than 1,000 people out of work in an area where unemployment already is one of the highest in the state. Fairchild has offered to give the plant to the state, which would give Fairchild a tax break and the state a chance to find a firm that would hire some of those about to be laid off.

The state is having an independent consultant look at the plant and has been talking to businesses about taking it over cheap.

"They're talking about the possiblity of doing some work to change the 727 from a three engine plane to a two engine plane," Hughes said. "That won't happen right now; they have to do some testing in California which could take from a year to 18 months. But wouldn't it be nice if they took over the plant in Hagerstown to do that kind of work."

However, a spokesman for Martin-Marietta said the company had no plans to take over the plant, and that the idea was "very speculative." Hughes agreed with that assessment.

Hughes is being pushed by key staff aides to accept Fairchild's offer of the plant and is leaning strongly in that direction. The company would like an answer from the state by the end of the year and Hughes staffers would like to have a commitment from someone to take over the million-square-foot plant before it gives Fairchild an answer.

On another topic, Hughes said that although he did not condemn three members of the General Assembly for a recent trip they made to South Africa, he would not have made such a trip himself either as governor or as a legislator.

"Obviously, I don't agree with some of the policies of that government and to accept such an invitation might be misinterpreted," Hughes said. "I see nothing wrong with going to South Africa, I don't think you only go to places where you totally agree with everything they're doing. I think you can learn things from such an experience. But I would not go under those circumstances."

Sens. Laurence Levitan (D-Montgomery) and Raymond E. Beck (R-Carroll) and Del. Tyras R. Athey (D-Anne Arundel) traveled to South Africa for three weeks with their expenses paid by the South African government.