The Northern Ireland Police Ombudsman is to launch an investigation into why the killers of Sunday World journalist Martin O'Hagan have yet to be charged, five years on from his death.

Colleagues of O'Hagan have named Loyalist paramilitaries believed to have been involved in his killing. And they fear that the Police Service of Northern Ireland has failed to prosecute them because at least some were informants for the security services.

This week O'Hagan's brothers and sisters made a formal request that Ombudsman Nuala O'Loan investigate the case — only family members of a murder victim can prompt an Ombudsman Inquiry.