Billionaire Sports Direct founder Mike Ashley has criticised recent cost of living and retail policies from AndyBurnham as "populist reactions".
In a letter to the prime minister, the entrepreneur accused him of "jumping on 'everyday fixes' or bandwagons", while "disastrous" business rates policies and increases to the cost of employing workers were causing businesses to struggle.
He also described a previous proposal of increasing business rates on large warehouses to help reduce them for pubs and clubs as "delusional".
A Downing Street spokesperson said Burnham would "build a new economy that backs British business, delivers growth in every postcode and ensures the essentials in life - like energy, water and housing - are affordable again."
Promises including cutting VAT from household electricity bills and reducing business rates for some firms is "just the start", they added.
Earlier this month, Burnham promised to revitalise Britain's "hollowed out" high streets by helping councils block new vaping and betting shops.
He also brought forward a plan to end subscription traps and ban shops using misleading recommended retail prices, which can make it seem like discounts are larger than they really are.
In Ashley's letter, seen by the BBC and first reported by the Financial Times, he hit out at announcements made since Burnham succeeded Sir Keir Starmer as prime minister.
The businessman called on Burnham to use his first Budget, scheduled for 27 October, to lower costs for employers and change the government's position on business rates.
Pubs, social clubs and live music venues will get a 20% business rates cut from April, while a review has been launched into how the tax, which high street firms have long called for reform to, is calculated.
"Shortsighted or populist reactions to underlying business challenges are not the answer," Ashley said in the letter.
Ashley has repeatedly called for a fundamental overhaul of the tax, including levelling the playing field between High Street retailers and online rivals.
"If your answer is to tax larger retailers even more, through hiking business rates on retailer owned or third-party warehouses whilst reducing rates for pubs and clubs, then that is simply delusional," he wrote.
Burnham previously said before he was prime minister that cuts for pubs, clubs and music venues could be paid for by higher levies on warehouses operated by online firms such as Amazon, and targeting the owners of empty high street properties.
Ashley built Frasers Group from a single Sports Direct store in Maidenhead in 1982 to a sprawling empire of dozens of brands employing 30,000 people.
The billionaire has frequently attracted controversy from investors and the media, with accusations over the years of building success by exploiting workers.
In 2016, Ashley admitted to MPs that workers at his Derbyshire warehouse had been paid below the minimum wage and a policy of fining staff for being late was unacceptable.
The business, still owned by Ashley but run by his son-in-law Michael Murray, this month bought luxury department store Harvey Nichols and promised a "significant restructuring" of the business.
Ashley also used his letter to ask Burnham how the prime minister intends to revive Harvey Nichols, which has faced financial challenges in recent years.
Referencing comments by Tory peer and former Marks & Spencer boss Lord Rose, who called the announcements "hot air", Ashley said "I agree with him".
"It is the disastrous business rates position (which I have raised many times over the years) and the dramatically increasing cost of employing people that are really causing business to struggle," Ashley said.
"You have the chance to make a difference or get it horribly wrong," he added.
Ashley said the High Street will be "further devastated" without major reforms, and warned Burnham's suggestion he will consider further business rates changes in the coming Budget are "too little, too late".
He also used the letter to attack Burnham's plans to clamp down on the use of recommended retail prices, saying instead the real issue is "price fixing in sporting goods and other markets" - where he cited the rising cost of official football merchandise.
