The letter will be published a fortnight after the organisers of a march in London to demand a second referendum claimed it was attended by 700,000 people.
The new campaign Business for a People's Vote has received more than 70 backers, including former Treasury minister Lord Myners, the co-founder of lastminute.com, and head of vehicle parts supplier Unipart.
Meanwhile, former prime minister Tony Blair has written in the Observer that MPs should "resist" agreeing to what may be labelled a "reasonable deal", adding: "There is the pointless, the painful or fudge through postponement of the core issues".
Britain voted in 2016 to leave the European Union, but some argue the public should get another chance to decide once the terms its departure and future relations with the European Union are clear.
'Each option is bad.
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The open letter warns that Theresa May's final exit deal will push Britain towards "a destructive hard Brexit". Now over 70 corporate chiefs have made a decision to get the band back together and are launching a group called Business for a People's Vote, an offshoot of the formal People's Vote campaign that rose from the ashes of the defeated Remain camp.
Sunday's letter has been co-ordinated by The People's Vote campaign group chaired by Roland Rudd, the City public relations chief whose sister, Amber Rudd, was the Home Secretary until earlier this year. They will be bad for business and bad for working people.
"The uncertainty over the past two years has already led to a slump in investment, which will make our country poorer".
The Prime Minister says asking people to vote again would be a betrayal of voters' trust, and this is true: the divisions that exist today would not be resolved by a second vote, they would be exacerbated.
A Department for Exiting the European Union spokeswoman said: "The people of the United Kingdom have already had their say in one of the biggest democratic exercises this country has ever seen and the prime minister has made it clear that there is not going to be a second referendum".
The UK's top lawyers have urged Theresa May and MPs to back a second Brexit referendum, saying that "democratic government is not frozen in time".
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