The announcement by Attur, a former minister, came a day after Shettar and other BJP leaders dismissed the threat to the government and also took a dig at the January 4 deadline set by Karantaka Janata Party supremo Yeddyurappa.
"I have decided to quit my assembly membership. I will be sending my resignation letter to the Speaker K G Bopaiah by fax and meet him in person on January five", Attur told the media in Basavakalyan in the company of Yeddyurappa.
said Attur will be the KJP candidate for the Basavakalyana assembly constituency in the next year election.
In the event of Attur's resignation accepted, the strength of the ruling BJP in the 224-member assembly comes down to 117 (including Speaker). The Congress has 71, Janata Dal Secular has 26, there are seven Independents and three vacant.
Yeddyurappa has already declared that his party would meet in Bangalore on January 4 to decide the fate of the Shettar ministry, the resignation of which he has been demanding.
There is no word yet from Yeddyurappa on how many MLAs and ministers will oblige him by resigning their membership ahead of the assembly polls expected to be held by April-May next.