Johannesburg - The vote of no confidence in President Jacob Zuma will be the most important and difficult ballot ANC MPs will have to decide on, the party's stalwarts said on Sunday.The stalwarts wrote an open letter urging MPs to remember the pledge they made as a members of Parliament - to never conduct themselves in a manner that will diminish their integrity and that of the Republic of South Africa."As you approach the moment of truth, please appreciate that the personal decision you make in this vote of no confidence, will not simply be judged in the weeks to come, but will be written into the history, not only of the country but that of the ANC, as an act that struck a blow for the rescuing of the ANC," the letter stated. Earlier on Sunday, Parliament said 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.The motion was expected to be heard and voted on in the National Assembly on Tuesday. The Constitutional Court ruled in June that Mbete, as Speaker, has the constitutional power to decide whether or not to hold a secret ballot during the motion.- Read more: Tuesday is D-day for Zuma, Parliament faces a showdownThe stalwarts said in their letter that the sanctity and security of the state was under direct attack from criminal politicians, state officials and privateers. "We are witness to larceny on a grand scale, leaving the country not only impoverished, but also increasingly in the hands of criminalised and compromised governance. "Whether our organisation can retain and regain the confidence of broader society will be determined by its ability to rid itself of the cancer of the political and economic corruption aided and abetted by key elements within the organisation." The stalwarts said a motion of no confidence in Zuma was an inevitable outcome of the countless scandals he had involved himself and his office in. "To replace the obligation of advancing the ANC’s historic mission with the burden of defending the unacceptable and indefensible is inconceivable, but sadly that is the reality you are confronted with." They said that the vote of MPs would come down to their own personal commitment to the country, and the ANC, adding that it would be a recognition that they are prepared to uphold, help and contribute to the restoration of the highest ethical standards and values society expects of the organisation and its parliamentarians. 8th motion of no confidence Zuma's eighth motion of no confidence comes amid intensified calls from within the ANC for him to step down from leadership. 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”.