Junior minister Finian McGrath has agreed to ask the Cabinet to revise the terms, so that the treatment of other victims is also included.
A special cabinet meeting is likely for later today to sign off on the revised inquiry.
It's meanwhile emerged that one person removed from the same care home had to be moved to Northern Ireland, because the local health board would offer no further care.
Fianna Fáil's John McGuinness says the child's mother met with legal threats when she raised concern about her child in 1992.
