Nelson H. Cruikshank, President Carter's counselor on aging, assailed the administration yesterday for its proposed cuts in Social Security benefits.

While Cruikshank was blasting the cuts, the House Ways and Means Social Security subcommittee, headed by Rep. J. J. Pickle (D-Tex.), concluded that even if it eventually approved some of the cuts, the action almost certainly will not come in time to take effect during fiscal 1980 as Carter has proposed.

In a virtually unprecedented performance for a sitting adviser to a president, Cruikshank told the House Committee on Aging that the proposed cuts are "ill-advised," "at the very least disingenuous," and "trumped up" to grab credit for a quick budget reduction.

He said they reflect "lack of understanding" of "the very nature" of Social Security and of benefit promises made to persons who have paid in all their lives. Cruikshank's views were in tune with those of a huge coalition of organizations, headed by former Health, Education and Welfare Secretary Wilbur J. Cohen, who also testified and said he will battle the cuts to the end.

Cruikshank said he was speaking for himself, not the administration, and he had been informed by the White House "that I am free to express (my) disagreement as long as I make clear the distinction between what are my own views and what are the administration's positions."

As proposed by the administration, the cuts -- which include phasing out the student benefit for orphans aged 18 to 21, eliminating the $122-a-month floor on benefits, reducing disability benefit levels and eliminating the $255 burial benefit -- would have saved $609 million in fiscal 1980.

Stanford Ross, the current Social Security Commissioner, defended the proposed cuts in later testimony. "None of our proposals affects the central elements of the Social Security program" or hurts current beneficiaries, he said, adding that the proposals seek only to keep program costs within reasonable limits by cutting elements of "relatively low social priority" or "random largess."

Pickle, at an organizational meeting of the Ways and Means subcommittee, said some of the cuts are so controversial that it is "neither realistic or practical" to expect passage in time for any savings in the fiscal 1980 budget, if ever.

He and the subcommittee made an exception for disability insurance provisions, which the subcommittee acted on last year. Pickle said disability cuts -- among a host of Social Security issues like coverage for federal employes and a hope-for postponement of the Social Security tax rate increase scheduled for 1981 -- are the only element likely to pass Congress in time to have any impact on the fiscal 1980 budget. Fiscal 1980 begins Oct. 1.

Therefore, the subcommittee agreed to inform the full Ways and Means and Budget committees that, of the $609 million proposed savings, the most that can actually be expected in 1980 would be $50 million to $75 million, by reduction of disability benefit levels.

Pickle said that in view of the coalition headed by Cohen and other factors, it simply is not practical to think of making any other major cuts soon.

But he said the subcommittee will study all major Social Security financing and benefit issues and perhaps might come up with a comprehensive bill of some type around the end of this year or early in 1980.

He said that as the scheduled tax increase -- from the present 6.13 percent rate to 6.65 percent in 1981 -- approaches, members may be more willing to consider changes in the system to reduce the tax increase.

Cohen, former Social Security Commissioner Robert Ball, former Social Security Chief Actuary Robert J. Myers (1947-70) and other witnesses all joined Cruikshank in attacking the proposed cuts.