Amanda Bynes blasted Lance Bass as an "ugly ex boy band member" for publicly declaring that he was scared for her, E! News reported Thursday.

The former 'N Sync member called into Las Vegas radio's Mark and Mercedes show Wednesday and commented on the public behavior of his friend. Bynes has been in a downward spiral for months which has included shaving her head and posting nude pictures of herself online. Her antics reached their peak when she was arrested May 23 for allegedly throwing a bong out her New York apartment.

Bass expressed worry for the 27-year-old actress. The two became friends when Bass produced Love Wrecked in 2005, which Bynes starred.

"No one is able to get to her," he told the radio station. "I'm actually really scared for her, and I hope someone is able to get to her to give her the help she needs."

Bynes responded Thursday on Twitter. She called into question why Bass assumed he was in any position to make any judgment on her life.

"I ignored Lance Bass on twitter and now he is saying I have a mental illness. Sorry you're an ugly ex boy band member w/ no talent or career," she tweeted.

Bynes followed up the tweet with another post. The former Nickelodeon star insisted that she had not spoken to the pop singer in years.

"I haven't spoken to Lance Bass in 11 years. To say I have a mental illness out of nowhere makes me lash out! You're making me crazy!" she wrote.

Bass responded to Bynes' assertions later that day. He pointed out that it had actually been seven years since Love Wrecked was filmed. Furthermore, he said that Bynes was just at his birthday party three years ago. Bass once again vented his frustration with the circumstances surrounding her.

"Ouch-The Amanda I know would never had said something like this to me-either this is a fake person or she really does have a mental illness. Way too sad. I reached out-all i can do," he wrote.

Watch a trailer for LoveWrecked below:

Tags: Amanda Bynes Lance Bass