Key business leaders and lobbyists, seeking some way to reduce future deficits without giving up their gains, are urging Congress to postpone the tax cuts it voted last year for individuals while preserving those it voted for corporations.

In the most visible example of this so far, Charls E. Walker, a major business lobbyist who was chairman of President Reagan's tax policy task force during the 1980 campaign and now serves on the president's Economic Policy Advisory Board, yesterday urged the House Ways and Means Committee to consider delay of the scheduled 1983 individual rate cut.

Separately, congressional staff aides said leaders of the Business Roundtable, an organization of the chief executive officers of the nation's largest corporations, signaled support for postponement of the 1983 individual cuts at a private breakfast meeting at the International Club here last week.

To date, Reagan adamantly has rejected suggestions that the 10 percent individual rate cuts be deferred.

In his testimony yesterday Walker, who noted his ties to the administration but said he was "testifying only for myself," told the committee:

"If additional revenues are needed to narrow future deficits, consideration should be given to delay--not suspension, only delay--of all or part of the 10 percent individual income tax cut scheduled for July 1, 1983.

"A delay of the entire tax cut for one year would raise revenues by an estimated $9 billion in fiscal year 1983 and an additional $27 billion in FY 1984. If the delay were extended until January 1, 1985, the FY 1984 deficit would be reduced by $37 billion."

Delay of the tax cut along with natural gas price decontrol and a severance tax that Walker advocates on gas would have a "dramatic" effect on financial markets, he contended.

A tax cut deferral would not be a violation of Reagan's economic program, Walker contended, because the individual cuts would be achieved within five years, the time period for the "game plan."

Walker has been a major proponent of the Reagan program, and he helped form an organization of business lobbyists known as the "Carlton group" that formulated the basic business tax cut--the so-called 10-5-3 proposal for speeding up depreciation allowances--that the president later incorporated into his Economic Recovery Act.

James Evans, chairman of Union Pacific Corp. and co-chairman of the Business Roundtable, also testified yesterday. He told the Ways and Means Committee that "revenue increases must also be considered" in order to lower the forthcoming deficits, but he did not mention postponement of the individual cuts.

Instead, he suggested possible excise tax increases, which the president earlier this year rejected.

Asked after the hearing about the suggestions made by Roundtable leaders at the closed breakfast session with congressional aides, however, Evans said postponement of the individual cuts also "should be explored."

During the hearing, Rep. Dan Rostenkowski (D-Ill.), the committee chairman, questioned whether the business lobbyists were "saying we should not cut business taxes, but we could cut individual taxes?"

Walker contended that reducing the business tax cuts "would have a very, very counterproductive effect." After the session, Evans supported Walker's views, arguing that any lessening of the business tax reductions would create "uncertainty" and would "deflect the very purpose" of the cuts to stimulate investment.

Both Walker and Evans were strongly opposed to strengthening the corporate minimum tax, a proposal advocated both by the administration and by Sen. Robert J. Dole (R-Kan.), chairman of the Finance Committee.

Walker argued that a minimum tax--legislation designed to prevent companies from using existing tax breaks to lower their tax liability below certain minimum levels--would weaken the investment incentives in the law.

Evans said that "there is substantial concern in the business community about the proposal for a corporate minimum tax."