Washington attorney Tyrone Brown, who earlier this week turned down the job, yesterday accepted a White House offer to complete the last 21 months of Benjamin Hooks' term on the Federal Communications Commission.

His nomination will be submitted to the Senate by President Carter as soon as routine background checks have been completed, it was learned yesterday.

Brown has reportedly been under intense White House pressure this week to reconsider his earlier refusal.

Although Brown would not comment on the report, it is understood that he has been assured of re-appointment to a full seven-year term when his current term runs out in June 1979.

It has been learned that Hooks, who resigned from the FCC last summer to accept the leadership of the National Association for the Advancement of Colored People, was one of several black leaders who had strongly urged President Carter to appoint a black to the full seven-year term made available when FCC chairman E. Wiley's term ended in June.

Instead, that appointment went to Charles D. Ferris, the 44-year-old general counsel to House Speaker Thomas P. O'Neill (D-Mass.) earlier this week.

Whether the lobbying by black leaders influenced Brown's initial decision to turn down the White House offer of Hooks' unexpired 21-month term is not known. Brown yesterday refused to comment on the reasons for his earlier withdrawal.

With the appointments of Ferris and Brown, the FCC will be restored to its full membership of seven commissioners. It gives the Democrats a majority for the first time since President Nixon's first term.

Brown, 34, is the former general counsel of Post-Newsweek Stations and currently is a member of Caplin & Drysdale, a tax law firm.

He was managing editor of the Law Review at Cornell Law School and later served as law clerk to then Chief justice Earl Warren. He is highly regarded at the White House and was one of the original top choices of the Carter administration for the FCC.