A THREAT by Western Cape Premier Helen Zille to take the public protector to court was a bullying tactic, the office of African National Congress chief whip Mathole Motshekga said on Monday.

"We believe that Zille's threat is nothing short of a political manoeuvre designed to bully the public protector and thereby send a chilling message to chapter 9 institutions that the party is untouchable," it said in a statement.

Thuli Madonsela, the protector, has reportedly found in a draft report that a Western Cape government tender awarded to advertising agency TBWA Hunt Lascaris in 2010 to centralise communications was invalid.

The report, leaked to the media a week before a deadline for the province's response, recommended that the contract be cancelled as it was entered into unlawfully. The draft report has led to increased calls for Ms Zille's resignation after she last year said she would resign if the tender was found to be "corrupt".

In a hastily organised press conference on Sunday, Ms Zille said the draft report was "fatally and legally flawed". If the draft report's "material errors in law" were not rectified, "we will take the findings on review to the high court", she said, and even all the way to the Constitutional Court.

Ms Zille said the leak was irregular and prejudiced the province's right to rectify the "material legal errors in the draft report, before the report was finalised".

"Without casting aspersions on the public protector herself, we believe this premature leak prejudices the administration of justice and compromises our rights," she said.

Ms Zille said attempts to contact Ms Madonsela had failed, and therefore the province had to go public with its case. She was at pains to point out that the draft report had found that "there was no corruption whatsoever nor any evidence of political involvement, interference or manipulation in the procurement process".

However, the report found that two of the six people on a tender bid evaluation committee - Ms Zille's special advisers, Ryan Coetzee and Gavin Davis - should not have been there. It found their involvement was unlawful, that the contract was rendered invalid and its termination was required.

The office of the chief whip said: "The legal threat ... sets a worrying precedent in that chapter 9 institutions ... may in future be forced to spend their budget allocations defending themselves in court against government institutions than on their statutory obligations."

It said it was "gravely concerned" because this underminded the public's respect, trust, and confidence in state institutions.

Also on Monday, the Western Cape branch of the ANC said it was shocked at Ms Zille's "desperate attacks" on Ms Madonsela.

"The ANC is alarmed that premier Zille is in breach of the confidentiality on the interim report, while at the same time it is shocked by her arrogant attitude," provincial secretary Songezo Mjongile said in a statement.

He said Ms Zille's attempts to circumvent and undermine the work of the public protector by intimidating and discrediting her was untenable.