Sewage spills into Belfast Lough are “pernicious, damaging and the time to act is now”, the UK’s environment watchdog has said.

The Office for Environmental Protection (OEP) is investigating two Stormont departments and the Utility Regulator over the number of spills.

Its Chief Executive Natalie Prosser told BBC News NI that Belfast Lough was in a position of “serious degradation” and not getting any better.

DAERA Minister Andrew Muir said the investigation was “sadly not unexpected” while the Department for Infrastructure has welcomed it.

The OEP will examine how the Utility Regulator, the Department for Infrastructure (DfI) and the Department of Agriculture, Environment and Rural Affairs (DAERA) regulate sewage discharges by NI Water.

Drainage in Belfast was designed by Victorian engineers as a combined system, where storm water and sewage use the same pipes.

Officials have previously warned of the threat sewage spills pose to the ecosystem of Belfast Lough.