An Alexandria man who had pleaded guilty to the statutory rape of his two teen-aged stepdaughters and was scheduled to be released from jail next week must remain in jail because an alcohol rehabilitation program refused to accept him, a city prosecutor confirmed yesterday.

The series of rapes, which occurred from 1972 to 1974, came to light this summer when the stepdaughters, now in their twenties, pressed charges. The elder stepdaughter testified in court that the man had fathered her daughter, who is now 10 years old.

The 54-year-old man was convicted in June of this year and began serving a one-year jail sentence soon thereafter.

Despite opposition from the stepdaughters and Assistant Commonwealth's Attorney Constance Frogale, Alexandria Circuit Court Judge Donald M. Haddock agreed last month to release the man from jail this coming Tuesday to enable him to receive intensive counseling for alcoholism.

Haddock ruled, however, that the balance of the man's jail sentence would be reinstated if the Arlington-based Alcoholics Rehabilitation Inc. program did not accept him; if he had any contact with his wife, two stepdaughters and daughter, or if he began drinking again.

Rebecca McPherson, executive director of the rehabilitation program, yesterday declined to say why the man was denied admittance.

J. Ronald Lynch, attorney for the jailed man, said that his client had been refused admittance because the rehabilitative center lacked necessary medical facilities. Lynch said he will file a request next week to have the man admitted to another rehabilitative program.

Frogale yesterday expressed satisfaction at the development. "It's more appropriate that he serve his full term," she said, adding that alcoholism did not excuse the crime. The maximum penalty for statutory rape -- sexual relations with a person under 18 -- is 20 years in prison.