Actress Kim Cattrall has lashed out at her former Sex and the City co-star Sarah Jessica Parker on social media.

In a scathing Instagram post the 61-year-old accused Parker of being "cruel" and disingenuous after the American star tweeted a message of sympathy following the sudden death of Cattrall's brother.

Last Sunday Kim shared the tragic news that Christopher Cattrall, 55, who was previously reported missing, had died.

Local police confirmed that her brother's body was discovered on his rural property in Blackfalds, Alberta, Canada. A cause of death was not given, but police said it was not considered suspicious.

Sharing the tragic news on Twitter, Kim wrote: "It is with great sadness that myself and my family announce the unexpected passing of our son and brother, Chris Cattrall."

"At this time we ask for privacy. We want to thank you all on social media for your outpouring of love and support in this trying time."

Her message sparked a flurry of tweets from concerned fans and friends offering their sympathy and support in the face of her loss. Among them was a tweet from Parker, which read: "Dearest Kim, my love and condolences to you and yours and Godspeed to your beloved brother. Xx."

My Mom asked me today “When will that @sarahjessicaparker, that hypocrite, leave you alone?” Your continuous reaching out is a painful reminder of how cruel you really were then and now. Let me make this VERY clear. (If I haven’t already) You are not my family. You are not my friend. So I’m writing to tell you one last time to stop exploiting our tragedy in order to restore your ‘nice girl’ persona. Copy and paste link https://nypost.com/2017/10/07/inside-the-mean-girls-culture-that-destroyed-sex-and-the-city/

A post shared by Kim Cattrall (@kimcattrall) on

While Kim had earlier turned to instagram to express her gratitude to her "fans, friends and my #SexandtheCity colleagues for the outpouring of support" in the aftermath of her brother's death, she later issued a stern rebuke directly to Parker, dismissing her friendship.

"I don't need your love or support at this tragic time @SarahJessicaParker," she wrote. "My Mom asked me today 'when will that @SarahJessicaParker, that hypocrite, leave you alone?'

"Your continuous reaching out is a painful reminder of how cruel you really were then and now. Let me make this VERY clear. (If I haven't already) You are not my family. You are not my friend. So I'm writing to tell you one last time to stop exploiting our tragedy in order to restore your 'nice girl' persona."

And in another pointed reference, she added a link to a New York Post article titled: "Inside the mean-girls culture that destroyed 'Sex And The City'."

The Instagram spat comes after Cattrall last year insisted that she would not star in a third Sex and the City movie. Speaking to Piers Morgan she addressed the rumours of a rift between the stars explaining that the cast of the hit series were "never friends", and adding that Parker "could have been nicer" after she turned down the chance to play Samantha for the third movie.

"We've never been friends," she said. " We were just colleagues and in some ways it's a very healthy place to be."

She further rejected claims allegedly made by Parker, that she had made unreasonable demands and behaved like a "diva", adding that the relationship between the two women had become "toxic".

She added: "I really think she (Parker) could have been nicer. I don't know what her issue is."

52-year-old Parker responded to Cattrall's remarks saying that she was "heartbroken" and that she recalled their time together quite differently.

Fans of the two stars took to Twitter to comment on the public war of words, with many defending Cattrall for her uncharacteristic outburst in a time of grief.