Delhi Chief Minister Arvind Kejriwal continued on Sunday to take potshots at Prime Minister Narendra Modi, saying he cannot act against the Gandhi family as they know his "secrets"."Sources- Gandhi family has some secrets of Modiji. That's why Modiji will never be able to act against any member of Gandhi family," Kejriwal posted on Twitter. Earlier, he had alleged nexus between Congress President Sonia Gandhi and Prime Minister Modi over the AgustaWestland VVIP chopper deal in which kickbacks were allegedly paid when United Progressive Alliance (UPA) was in office. He had also dared the prime minister to arrest the Congress president.Kejriwal's Aam Aadmi Party (AAP) had on Saturday organised a demonstration here demanding the arrest of Sonia Gandhi who has been under fire after her name appeared in an Italian court's judgement about AgustaWestland deal last month.