The Health Service Executive has formally apologised to an intellectually disabled woman who it allowed to remain in a foster home for over 13 years despite allegations of physical and sexual abuse at the facility.

The letter of apology comes less than a week after the HSE told the Public Accounts Committee it had already apologised to the young woman and to her mother. But the mother and others deny this.

The latest twist in the foster home abuse scandal in the southeast came when a PAC source told RTÉ News that, on Monday, a senior HSE official had issued a written apology to the profoundly disabled woman.

Her social worker, a whistle-blower in the case, has raised claims that the woman - who was placed in the foster home between the ages of 11 and 31 - was subject to severe sexual and physical abuse and that, despite a former resident's warning in 1995, she was left there for a further 13 years.

After last week's committee evidence about a disputed HSE apology, the report of this week's written apology was confirmed in a HSE statement last night revealing that a formal letter apologising for significant failings in care was issued on Monday to the disabled woman and to other relevant parties.

The HSE explained that while it had acted in good faith, a regrettable misunderstanding had arisen about the nature of the apology it had already offered and that to remove any doubt, its representative had met the CEO of the woman's service provider and had issued the formal apology.