Melbourne - Speaking to the SkySports website, former Australian spin legend Shane Warne has accused Mickey Arthur of "sour grapes" after the SA-born coach sued Cricket Australia (CA).Warne lashed out at the former Australia coach’s R40 million claim against his former employers, after court documents containing highly inflammatory claims from Arthur, were leaked to the press.Warne said that Arthur should be "very grateful" for having been given the opportunity to coach Australia in the first place."He did the best he could do and put his heart and soul into it so it sounds (like) a bit of sour grapes to me," Warne said."If that's your gripe, go behind closed doors, but I think he should sit back and be quiet as A$4 million is out of order."It is very disappointing that he wants money and perhaps he should go back to homework-gate and start writing some lines and send some papers to Cricket Australia."Australia won just 10 of Arthur's 19 Tests in charge, suffered a 4-0 series defeat in India and failed to reach the knock-out phase of the 2013 Champions Trophy.Warne said the decision to fire Arthur and appoint Darren Lehman in his place had been the right call by Cricket Australia."Cricket Australia were very proactive when it wasn't working and unfortunately when things aren't working and you are the coach you are the first to go," added Warne."It's you or the captain and Australia weren't going to get rid of Michael Clarke so Arthur had to go."I am one of Cricket Australia's harshest critics but you have to give them ticks for appointing Lehmann; it was a fantastic move as even though Australia lost (the first Test) they have shown better spirit."Earlier this year, Warne sent a much-publicised open letter to Cricket Australia recommending Arthur’s axing, while the South African was still coach of Australia.