The police ombudsman's office in Northern Ireland has received a complaint that police did not properly investigate a witness statement made concerning an allegation of child sex abuse in the Liam Adams case.

Liam Adams, Sinn Fein leader Gerry Adams' brother, was convicted last week of raping his daughter Aine in the 1970s.

Now a complaint has been lodged that is reportedly linked to Gerry Adams' role in giving evidence.

Speaking during Northern Ireland Assembly question time this week, Health Minister Edwin Poots welcomed the conviction of Liam Adams, but he added that the Police Service of Northern Ireland (PSNI) still have questions to answer.

Poots, a member of the hardline Democratic Unionist Party (DUP) said he believed that abuse victim Aine Adams had been let down by the RUC, as well as by her uncle Gerry Adams and by the PSNI.

In response to recent statements Gerry Adams said he was aware he had committed no offence over the case.

According to the BBC the North’s attorney general will shortly review a decision not to prosecute Gerry Adams for allegedly withholding information on his brother.

But Adams has repeatedly said he had co-operated fully with the police, the Public Prosecution Service and the courts.

Nonetheless Poots said he believed the Police Ombudsman should examine the PSNI's handling of the matter. Poots also said there should be ‘zero tolerance’ for those who cover up child abuse.

Adams made his first report to the police about the abuse allegations in 2007, shortly after his party voted to accept the legitimacy of the Police Service of Northern Ireland.

Adams said this week that he took exception ‘to a quite despicable lobby that's going on’ over the case and said there was ‘quite contrived reaction in some quarters.’

‘I learned that the DUP, at least some of the DUP, and indeed some in Fianna Fail, are coming at this in a political way,’ he said.