Contostavlos reacted after Dappy retweeted a message from a fan saying: "Not hating on tulisa but she should really step up and at least ask @TheDappy if he's okay..I think he's having a hard time.x love you bothx."
Tulisa then wrote on her official Twitter page: "@TheDappy u know my number mate..I dont know urs cus u aint gave it 2 me since u changed it... so dont gass the fans, u wana talk Im here (sic)."
The 23-year old then issued a warning to her cousin, writing: "@TheDappy serious man I hold it down, dont make me start talkin real cus u won't like it nor will the fans, allow twitter,man up n call me."
Continuing her rant, Contostavlos then revealed that N-Dubz have parted ways because Dappy left the trio, stating: "4 the ndubletts triena take sides... pls remember... dappy left ndubz, that's y we split, n wen he wanted 2 get away I tried 2 move him... In2 my yard (sic),
"But he left n got a new num n I aint heard from him since, he aint called or made contact, just talks 2 the press about me... Sayin he misses me but where the hells my call,I don't even have his num!had 2 txt me dad 2 pass a message 2 him n got no reply."
She then told her followers: "So pls don't let @TheDappy gass u up cus he knows what it is...I will kill 4 him n he knows it..but ask him the last time he tried 2 call me.
"@TheDappy dont reply 2 me by tweet,pick ya balls up n call me,I got a new place,cum stay,but dont b an ass on twitter..wen u know the deal."
Tulisa then tried to justify her rant, tweeting: "F this,cant believe I stooped so low as 2 have a private debate on twitter,but I aint havin no1 turn ndubletts against me over b*****ks.
"Said my piece on dis s**t n not doin it again...believe what u want after that but don't judge me on lies...sum1s gone below the belt 2nit (sic)."
She added: "My twitter,my thoughts..dont like,unfollow,dont care about media or oppinions..HATE ME,LOVE ME but base ur judgement on the truth #ispeakit... Goodnight x"
Dappy has since seemed to ignore Tulisa's messages, with a series of tweets instead emerging on the official N-Dubz account, stating: "*sigh* Whatever happens in the future I love each and every one of you that has supported us all.
"U lot say we are an inspiration 2 u but u guys r the biggest inspiration 2 me."