Prospects are growing bleaker day by day for congressional approval of legislation altering American Telephone & Telegraph Co.'s landmark divestiture agreement with the Reagan administration.

Parliamentary maneuvering in the House Energy and Commerce Committee yesterday stalled consideration of the bill so much that the committee adjourned for the July Fourth recess with its deliberations far from complete.

Congressional aides and telecommunications industry officials predict the committee will have an increasingly difficult time getting the controversial legislation through Congress before the end of the session--a session complicated by numerous election-year recesses for campaigning and by the reluctance of members to vote on quarrelsome issues.

The committee's failure to approve the bill before the July Fourth recess "may not have been the legislation's death knell yet, but it sure does hurt its prospects," one House source says.

Committee aides who strongly support the legislation said yesterday they are still optimistic that they can get it through this year. But just two weeks ago, the same aides were saying it was mandatory for the committee to complete its consideration of the legislation before the July Fourth recess if the bill was to get through Congress in 1982.

Given the parliamentary delays, it is unlikely that the committee will complete action on the measure before late July. After that, the House Judiciary Committee will have a chance to review the bill, Rep. Timothy Wirth (D-Colo.), the measure's chief sponsor, announced yesterday.

Then the measure won't come before the full House until September at the earliest, when other pressing measures, including taxes, will be vying for Congress' attention.

"Time and AT&T are our two worst enemies," Wirth said.

AT&T strenuously opposes the legislation, which restricts the Bell System more than the Jan. 8 divestiture agreement. Although the legislation mirrors the settlement in requiring AT&T to divest itself of its 22 local operating companies, it goes farther by requiring AT&T to set up a separate subsidiary for its long-distance network, which is now just a division of AT&T.

The legislation also changes key elements of the settlement by giving the divested local operating companies greater freedom to offer a variety of telecommunications services that the companies are barred from selling under the settlement.

AT&T has argued that the settlement should be approved by a federal judge first and then implemented before Congress acts. However, most of AT&T's competitors, state public utility commissioners and consumer groups are pressing for the legislation, saying it is needed to protect AT&T customers from sharp rate increases.

Supporters of the legislation are confident they have the votes to get the measure through the Energy and Commerce Committee.

Thus, the parliamentary stalling tactics are the key strategy for those who oppose the bill.

Yesterday, opponents led by Rep. Tom Corcoran (R-Ill.), refused to allow a series of technical, noncontroversial amendments to be adopted in a block.