The Democratic Alliance (DA) will not be deterred by "the African National Congress's (ANC's) plans" to disempower it through an orchestrated campaign to make the Western Cape "ungovernable", Premier Helen Zille said on Friday.

"We have been through this all before and survived. Upset by, and unable to accept, its defeat [in the Western Cape] at the polls on 22 April, the ANC is trying to undermine the Western Cape government.

"It did the same thing when it lost control of the City of Cape Town in 2006," she wrote in her weekly newsletter as leader of the DA.

"Even so, we will continue to point out and loudly condemn the attempts to dislodge us from power or to reduce our functions, which we have a legitimate mandate to fulfil," she said.

Some of those moves came dressed in legal garb, and they took the form of greater centralisation of power.

"In fact, just three weeks into Jacob Zuma's Presidency, there are disturbing signs that one of the most destructive trends of [former President] Thabo Mbeki's reign - towards the centralisation of power - is being revived and intensified," Zille said.

That was ironic, given that one of the main reasons for the deep anger and resentment directed towards Mbeki by Zuma's faction, which led to Mbeki's defeat at Polokwane and eventual recall as President, was Mbeki's sustained efforts to centralise power - both in the ANC and the State.

Three developments were of concern.

Firstly, the Public Service and Administration Minister Richard Baloyi had promised to reintroduce the shelved Public Service Amendment Bill, which would create a "single public service".

Secondly, Sicelo Shiceka, the Minister of Governance and Traditional Affairs, had indicated that the future of the provinces hung in the balance.

He was part of a team busy finalising a report that, in his own words, was "looking at the future of provinces, whether they will exist or not".

Thirdly, the national government looked set to gain greater powers to intervene in provincial and local government through the Ministry of Performance Monitoring and Evaluation and the National Planning Commission, both of which were new and located in the Presidency.

"Coming so soon after Cabinet's decision to approve the draft Constitution 17th Amendment Bill, which empowers national government to usurp powers from local government, these are worrying developments."

If they came to fruition, they would rip up the foundations of the "three-sphere" system of government enshrined in the Constitution and make a mockery of the constitutional principle of cooperative government, Zille said.