In what was called a preview of the 1988 political debate, Sen. Gary Hart (D-Colo.) and Rep. Jack Kemp (R-N.Y.) traded jabs and punches over their unconventional economic policy proposals yesterday, with both politicians sounding impatient to start that race now.

Hart -- who appeared with Kemp at an American Enterprise Institute conference on industrial policy -- had no kind words for the current campaign between President Reagan and Democratic presidential nominee Walter F. Mondale.

"Old ideologies produce irrelevant debates" about the nation's economic problems, said Hart. "Old debates obscure new realities, very few of which, unfortunately, are being addressed . . . in the political arena this year."

What the candidates aren't discussing, he said, are the government policies that he contends will be necessary if the United States is to compete successfully in a tougher international arena with "more organized industrial societies" in Europe and the Pacific.

Like other speakers at the AEI conference, Hart and Kemp disagreed at the outset over whether the United States has a competitive problem in trade. Hart argued that U.S. semiconductor firms are losing market share to foreign competitors, citing this as an example of a high-technology industry that needs government incentives and aid to get its inventions into the marketplace more rapidly.

Kemp jumped in, interrupting Hart: "That entrepreneur does not need a government agency to tell him or her" what to do.

"We are not losing the market to the Japanese in semiconductors," Kemp added (wildly misstating the industry's current research and development goal in memory capacity, in an apparent slip of the tongue).

Kemp said the current strength of the economic recovery is testimony to the success of the Reagan economic program with its roots in the tax-cutting philosophy Kemp has championed. The way to "soak the rich" is not to levy a special surtax on them, as Mondale has proposed, Kemp said, but to cut their taxes. Kemp and other supply-side advocates assert that with lower tax rates, the wealthy would shield less of their income from taxation through tax shelters and invest more in beneficial economic development -- ultimately generating greater tax revenue.

The auto industry doesn't need government protection, as Mondale has called for, or industrial policies involving unions, management and government, as Hart proposes, Kemp said. It needs to sell 10 or 11 million cars annually rather than the 8 million-plus U.S. car sales projected for this year, and he promised that further tax cuts would make this happen.

Hart, at the beginning of their debate, seemed to want to draw parallels between his new ideas and Kemp's, saying that there are similarities of views among "newly elected" officials of all parties about the necessity of stimulating faster, non-inflationary growth. And he joked that he and Kemp ought to take a "Jack and Gary" show on the road.

But Kemp was having none of it. "It's very tough to figure out" where he and Hart disagree, Kemp said, accusing Hart of advocating inconsistent policies.

Hart replied that he and Kemp "don't speak the same language." Kemp, said Hart, "believes growth solves all problems. I don't believe so." There must be growth "with a purpose," with government seeing to essential human needs and high-priority public investments, Hart said.

"No serious economist" agrees with Kemp that the current federal budget deficits can be reduced to appropriate levels without additional taxation, Hart said.