Allen on leave until investigation over

Richard V. Allen has asked for and apparently received permission from President Reagan to go on administrative leave from his position as national security adviser until the FBI inquiry relating to his handling of a $1,000 thank-you fee from Japanese journalists is finished.

Mr. Allen, in responding to questions on the NBC television program ''Meet the Press,'' said that there were no ''allegations of wrongdoing,'' only ''innuendos'' of wrongdoing, in his failure to turn over a $1,000 payment to President Reagan's legal counsel. He said he had fully intended to be rid of the money. And he acknowledged that he was guilty of ''bad judgment'' in failing to do so.

Allen said that in the confusion surrounding that first day in the White House, he simply had failed to write a letter to accompany the cash and send them both along to the counsel. After that, he said, he had forgotten it. ''I should have dictated a letter immediately,'' he said.

Asked about published reports indicating that the envelope containing the fee had a $10,000 marking on it, Allen said there were no markings on the envelope when he saw it.

''I fully expect to resume my duties,'' Allen told the reporters. He indicated he was certain that the Department of Justice probe would clear him.

However, Allen did not say whether Reagan wanted him back on the job if such clearance came along: ''I wouldn't want to characterize in any detail my conversation with the President.''

Allen said he didn't expect that a special prosecutor would be appointed by Attorney General William French Smith. However, he said that should this occur, he would remain on administrative leave.

He said that the President ''agrees'' with his decision to go on administrative leave. In his absence, Allen said his deputy, Adm. James Nance, will perform his duties.

Asked if he thought that after this investigation he could still serve the President well, Allen said: ''Yes, there is no reason why I could not resume my duties and perform at the same level as before.''

Allen was asked about his relationship with former associates and clients from the private consulting firm that he sold to former Reagan aide and speechwriter Peter D. Hannaford. Allen disclosed that he no longer has any interest in the firm, since Hannaford has paid the full purchase price for the company.