The African National Congress (ANC) is determined to prevent the Democratic Alliance (DA) from introducing its policies in the Western Cape, DA leader Helen Zille said on Friday.

Writing in her weekly newsletter, Zille said this was the real reason for the ANC's renewed threats to further centralise control over all spheres of government. Reaction to the threats had been surprisingly lethargic, she said.

Some commentators had supported the move, but criticism had been muted, with even staunch defenders of the Constitution unusually ambivalent.

"Why is this? At least part of the reason, is the erroneous belief that provinces have very few powers, and that it would make little difference if they are changed or scrapped".

This myth had become firmly rooted, which was wrong. Provinces had substantial powers. Provinces were a sphere of government with the power to make policy and pass laws on a range of issues, including education, housing and health, Zille said.

Even in "concurrent matter", in which jurisdiction was shared between national and provincial spheres, national policy and law could only trump provincial policy and law under specific and limited circumstances.

Because no province had used these powers since 1994, did not mean they did not exist.

"And, throughout the recent election campaign, the DA made it clear that if we won at provincial level, we would use provincial powers to put our policies into practice.

"I have little doubt that this has given impetus to the ANC's plan to curb the powers of provinces. They are determined to prevent the DA from translating our policy platform into a coherent legislative and delivery programme," she said.

"If the DA succeeded in doing this, we would be able to demonstrate our alternate approach to governance, and show that it benefits everyone.

"This would rob the ANC of its last remaining weapon against the DA - to cast us as a party of racists.

"The ANC's real motive is to control all levers of power and prevent the DA implementing our electoral mandate where we win elections."

The arguments being advanced by the ANC as reasons for changing or scrapping the provinces were spurious and "mere fig leaves", she said.