A White House spokesman said today the Reagan administration still hopes to convince investors in the shaky stock market that its economic program will work. Deputy Press Secretary Larry Speakes, asked about Wall Street's reported continued misgivings about the economic program, said, "We are still hopeful tht they'll be convinced . . . that we do mean business" in lowering inflation and eventually interest rates.

"They weren't convinced we could get the thing passed, and we got it passed," Speakes said. "So now they've got to be convinced it'll work."

The spokesman said the White House had "no plans for any fullscale blitz or anything like that to try to bring Wall Street around. I think Treasury Secretary Regan has a continuing series of meeting with influential people that he does present our message to." Asked what administration officials consider to be the reason for Wall Street's skepticism, Speakes said, "I think Secretary Regan has a complex explanation about bond traders dealing with the day-to-day and hour-to-hour business and that's what drives the interest rate up, holds the interest rate up."

In earlier briefings, Speakes had blamed the most recent stock market slump on unfavorable news about the national money supply and on a congressional estimate of upcoming government deficits $20 billion above the administration's estimates. Speakes said that the Treasury is working to smooth out the growth of the money supply and that the administration simply rejects estimates of a higher deficit other than the $42.5 billion already projected.