The House Ways and Means Committee yesterday ignored President Reagan's efforts to forestall protectionist legislation and approved a bill that would curtail textile imports by as much as 40 percent.

The bill's prime sponsor, Rep. Ed Jenkins (D-Ga.), said the presidential trade blitz and Reagan's threat to veto the textile bill had failed to cut support for the measure. He said the bill could reach the floor within 10 days as the vanguard of a host of trade bills being pushed in Congress.

"It has not affected my support in the House thus far," Jenkins said of the president's recent moves, including more aggressive action against unfair trade practices by other countries, a $300 million war chest to counter subsidized export financing, and coordinated intervention with leading industrial nations to lower the value of the dollar.

Despite Jenkins' confident words, there were signs of some erosion of support for the bill, which has more than two-thirds of the House members as cosponsors. An amendment by Rep. Richard A. Gephardt (D-Mo.) that would have severely weakened the measure, for instance, failed by just one vote -- 18 to 17 -- in the Ways and Means Committee yesterday.

On the Senate side, a major roadblock emerged to attempts to attach a similar bill to a little-known piece of legislation that allows the Defense Department to renew its lease on Kwajkalein Atoll, the major target for MX missile tests.

The Reagan administration has indicated it will veto the textile measure or any bill to which it is attached, even if it means rejecting legislation the White House eagerly seeks, such as the Micronesia Compact that contains the Kwajkalein Atoll provision.

The bill was due to go through the Senate this week, before the lease expires on Monday, but has been held up because of the dispute. The White House and the Republican leadership of the Senate were reported to be trying to negotiate a compromise with the major sponsors of the textile bill, South Carolina Sens. Strom Thurmond (R) and Ernest F. Hollings (D).

Thurmond was described as "determined" to get the bill on the Senate floor as soon as possible, and picked the Micronesia measure as the best, fastest vehicle. He is also a strong supporter of the Defense Department, and there was speculation that he might be persuaded to use some other bill to get the textile measure to the floor.

Thurmond had softened the textile bill considerably from its original version in an apparent attempt to avoid a presidential veto. The major change in the new bill cuts back the number of "major exporting nations" that would take the brunt of the measure's impact from 12 to three -- Taiwan, Hong Kong and Korea.

This saves two key countries from the effects of the bill: China, which has threatened to retaliate and with whom the Reagan administration is trying to build better relations, and Brazil, the world's largest debtor nation.

The amended Thurmond bill, introduced Wednesday night, does, however, include provisions to protect domestic shoe manufacturers, who lost out last month when the president overruled a recommendation by the International Trade Commission to grant that industry import relief.

Jenkins told the Ways and Means Committee that the textile bill is needed to keep domestic manufacturers from being driven out of business by a flood of imports, which increased 32 percent last year and is expected to rise by 25 percent in 1985, according to industry figures.

It is being pushed by a strong labor-management coalition from the textile and apparel industry. Opposition to the bill has intensified recently, sparked by retail organizations that say it will increase prices of clothing and toys, and by farm groups concerned they will take the brunt of any retaliation.

The bill would affect the 12 major exporting countries -- all Third World nations, largely in Asia. The three leading exporting nations are Taiwan, which holds 13.64 percent of imports to the United States; Korea, with 11.16 percent of imports, and Hong Kong with 10.55 percent of imports. Western Europe and Canada, whose exports are lower on the list, will not be touched despite recent increases in shipments of textiles and clothing from those countries.

The bill passed over the objections of Committee Chairman Dan Rostenkowski (D-Ill.) and Rep. Sam Gibbons (D-Fla.), chairman of the trade subcommittee, who called the legislation "a mistake."

"It's an honest mistake, but the history of our country is full of honest mistakes made by well-intentioned people," said Gibbons, who cradled a tiny pink made-in-Taiwan teddy bear as he addressed the committee.