A poll of entrepreneurs and executives revealed that just 26% believed the party was “pursuing business-friendly policies”, with almost one in six (57%) disagreeing.
Two-thirds (66%) said they regarded the Conservatives as traditionally pursuing policies that “increase prosperity and help well-run businesses”.
The survey of more than 1,000 people carried out for the People’s Vote, which wants a second Brexit referendum, found that even those whose businesses did no export trade with the EU were split 50-50 in terms of Leave v Remain.
Among those whose turnover was more than 10% derived from EU exports, it rose to 70-30 in favour of Remain.
Overall the split was 59-41 for Remain, with a similar split, 57-43, supporting a new referendum once “don’t knows” were removed.
Mr Grieve, the former attorney general and pro-Remain MP who backs another vote, said: “This poll highlights the extent that the Conservative Party is jeopardising its reputation for economic competence with the business community as a result of the way Brexit has unfolded.
“This should be a wake-up call because our party is risking everything for which we have always stood.
“Those sections of the party which are guided by the ideology of Brexit have only served to damage the ability of the Government to get any positive outcome from these negotiations.”
YouGov polled 1,004 people for the People’s Vote between September 18 and 26.
More than four in 10 (43%) said life had become harder for their business since the referendum, with just 9% saying it had become easier.
Almost three-quarters (73%) believed Britain would get a bad deal and 64% said they believed that would be the fault of the Government.
Almost two-thirds of the business leaders said they would rather trade freely than control immigration.
Melvin Benn, the managing director of Festival Republic, which is behind some of the UK’s largest music events including Reading and Leeds, Download, Latitude, V Festival and Wireless, said Brexit might damage the UK’s “cultural diversity”.
He said: “Every year the festivals I run welcome artists and performers from across Europe and the world.
“They benefit from our open borders but also love the tolerant and inclusive country which we have become.
“A hard or no-deal Brexit would not only create worrying commercial difficulties for my industry, but would cripple the economy and potentially strand our artists at passport control when they should be striding on to the main stage.”