Johannesburg - Parliament says Speaker Baleka Mbete is likely to announce her decision on Monday on the use of a secret ballot in this week's motion of no confidence in President Jacob Zuma. Parliament spokesperson Moloto Mothapo told News24 on Sunday morning that an announcement was likely to be on Monday, but the office would confirm later on Sunday.The motion is expected to be heard and voted on in the National Assembly on Tuesday. In June, the Constitutional Court ruled that Mbete, as Speaker, has the constitutional power to decide whether or not to hold a secret ballot during the motion. Mbete previously said she would make her decision known before the August 8 vote. - Read more: Tuesday is D-day for Zuma, Parliament faces a showdownOpposition parties have urged ANC members of Parliament to join in their motion of no confidence against Zuma. Mbete told the Sunday Times this week that she was going to make the decision on Monday, and that she was under immense pressure over her "difficult" decision. She also denied that she was employing delaying tactics. Economic Freedom Fighters leader Julius Malema told News24 last month that his party had already prepared legal papers to interdict Mbete should she refuse to allow a secret ballot. 'Nuclear bomb'Zuma's eighth motion of no confidence comes amid intensified calls from within the ANC for him to step down from leadership.The ANC has said that any of its MPs who vote in support of the opposition's motion of no confidence will face disciplinary action, with secretary general Gwede Mantashe earlier labelling it the "worst betrayal".ANC Chief Whip Jackson Mthembu said on Friday that voting in favour of the motion of no confidence in President Jacob Zuma would be like “throwing a nuclear bomb at the country”."The removal of the president will have disastrous consequences that can only have a negative impact on the people of South Africa," he told reporters at Parliament.