President Carter will send to Congress in the next few days a larger economic stimulus package for this year and next than he originally considered, including $50 per person rebate of last year's income taxes.

Those on Social Security and those whose income isn't enough to require them to pay taxes also will get $50 each.

These details were revealed yesterday by Bert Lance, director of the Office of Management and Budget. He estimated the total stimulus package at $3.13 billion, compared with a range of $23 billion to $30 billion announced Jan. 6 in Plains, Ga.

But other Carter administration sources warned that the exact dimensions of the package were not yet fixed, but said specifically that the tax rebate for 1977 will be larger than the $11 billion figure mentioned by Lance.

Meanwhile, at the White House, Carter told Democratic congressional leaders that the stimulus this year must focus heavily on the tax rebate rather than public-works programs that many members of Congress have been pushing.

Rep. John Brademas (D-Ind.) told reporters Carter had said that "a tax rebate in the first year is the best way because it's the fastest way to stimulate consumer purchasing power, and then we can act on public works."

But the new President did respond to pressures from business leaders to broaden that part of the package relating to business tax cuts by giving them the option of an additional 2 per cent investment tax credit.

A number of representatives and senators, backed by organized labor, said yesterday they will still try to deemphasize tax cutting in favor of larger direct expenditures for job creation. "There will be a fight on this," AFL-CIO lobbyist Andrew J. Biemiller told the Associated Press.

But neither Sen. Russell B. Long (D-La.) nor Rep. Al Ullman (D-Ore.), chairmen, respectively, of the tax-writing Senate Finance Committee and House Ways and Means Committee, said he had problems with the tax proposals. Ullman said, "You can do only so much in jobs."

Lance said the President "has not yet signed off on the tax package," but the thrust of his observations was that Carter had already opted for the higher numbers, stressing tax cuts in his first year in office and jobs programs in his second. A program as small as $23 billion is now officially dead.

Economists point out that the thrust to the economy from a $30 billion or $31 billion program could be considerable, because it covers only 18 months - from the first probable effective actions in late March or April through fiscal 1978, which ends Sept. 30, 1978.

The average annual rate of the package would thus be around $20 billion, or the equivalent of $40 billion if it were continued for a 24-month period.

Originally, the cost of the tax rebate was put at $7 billion to $11 billion, but Carter's proposal will exceed even the higher end of the range because his advisers think the economy needs that much of a quick stimulus.

According to authoritative sources, the recent cold wave slowing business acitivity in some sections of the country was not a major factor in this decision.

Precise details of the tax rebate have not been refined, Lance said.But the basic plan is for a $50 rebate for each exemption claimed by a taxpayer on last year's federal tax return. Thus a family of four would get a rebate $200, perhaps in April.

Taxpayers in middle-income brackets also would benefit by an increase in the standard deduction (to $2,400 for single persons and $2,800 for married couples). Adjustment of withholding rates during calendar 1977 would provide another $100 to $150 in tax relief for most taxpayers.

The budget chief promised there would be an effort to provide a $50 cash payment to those on Social Security and to low-income persons who do not pay taxes. But he added that "there may be a problem in reaching" people in the lowest income brackets.

The figures mentioned by Lance also implied that Carter's proposals for public-works spending, originally stated as $5 billion $8 billion for 1978, also wll be at the upper end of the range set in Plains.

One specific change in the Carter package relates to a tax break for business firms.

In the original proposal, corporate income taxes were to have been reduced $2 billion by a novel method: business owners would take a credit of 5 per cent of their contributions to the Social Security trust fund against their normal tax liabilities.

This device was selected instead of an alternative business stimulus, a proposal to increase the investment tax credit by 2 per cent to a total of 12 per cent.