Billionaire rag trader Solomon Lew has again taken aim at troubled department store Myer, saying the company's entire future is at risk and warnings investors to brace brace for a fourth profit downgrade in coming months, as well as significant losses come September.

The chairman of Premier Investments, Myer's biggest shareholder, again called for the dismissal of executive chairman Gary Hounsell, who on Wednesday revealed another disaster, with sales down 3.1 per cent in the 13 weeks to the end of April. This decline came despite the big discounting program that Myer has been running for the past three months, Mr Lew added.