The centralisation of power that a merger between the metro police and SA Police Service would create must be opposed, the Democratic Alliance said on Sunday.

"The ANC is obsessed with the idea of a centralised state, with power vested in the hands of a few at the heart of government," said DA shadow police minister Dianne Kohler Barnard in a statement.

"Accompanying that idea is the notion that anyone or anything opposed to that drive stands in opposition to liberation and must be brought into line."

On Saturday the police department said the country's metro police service was to be integrated into the SA Police Service to form "one super police force".

The project, spearheaded by Deputy Police Minister Fikile Mbalula, would see the SAPS transformed into a paramilitary force, with military ranks and discipline, said spokesman Paena Galane at the time.

He said the move was also in line with the resolutions taken by African National Congress at its Polokwane conference in 2007 to establish a single police service.

Galane said the initiative was still being discussed internally. On Sunday, Kohler Barnard said metro police had a function distinct from that of the SAPS.

"The very purpose of the metro police is to manage civic functions, which require a very particular and localised management structure."

They managed tasks including traffic offences and enforcing municipal by-laws, in exchange for rates paid.

"Outsourcing these kinds of things to the national government would be like putting the minister of co-operative governance in charge of making sure your pavement lawn is mowed.

"The DA will vigorously oppose this move on every level and with every means available to us," she said.