Just Group said in a terse statement on Monday that its board considered that John Cheston "has engaged in serious misconduct and a serious breach of his employment terms and, on that basis, his employment has been terminated today."
The statement did not elaborate further.
Mr Cheston did not immediately return a message sent to him on Linkedin.
Lovisa has also been approached for comment.
In June, the Sydney-based jewellery chain named Mr Cheston as its next CEO.
He had a 12-month notice period at Smiggle and was set to start at Lovisa on June 4, 2025.
There was no indication Monday morning that the start date was changing.
Just Group is a wholly owned subsidiary of Solomon Lew's Premier Investments which also owns Peter Alexander, Just Jeans, Jay Jays and other apparel brands.
It is in the process of spinning off Peter Alexander and Smiggle into new ASX-listed entities.
Mr Cheston also had an acrimonious departure from Country Road, the men's and women's clothing retailer he led for less than three months before leaving in 2010.
After his cessation of employment, Mr Cheston sued the company in Federal Court, with Country Road eventually agreeing to pay him $1.1 million in a settlement.
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