The Lord Mayor of the City of London will add his voice to a growing chorus of business leaders urging Theresa May to strike a Brexit deal with the EU before negotiations draw to a close.
In a speech prepared for the Bankers and Merchants Dinner at Mansion House on Thursday evening, Andrew Parmley will stress that a Brexit deal which ensures access to the EU single market is "vital" for City businesses.
"The City Corporation remains firm that access to the single market is a priority. For the firms I represent, and the millions they support, a deal is vital.
"We seek a bespoke agreement with the EU for reciprocal market access, based on the principle of mutual-recognition of our regulatory regimes.
"A bonfire of regulation would have no benefit."
Mr Parmley's comments will be the latest that run counter to Prime Minister Theresa May's mantra that "no deal is better than a bad deal" when it comes to negotiations with the bloc, raising concerns that the UK will have no replacement for passporting rights that ensure access to the single market for financial services after Brexit.
Other sectors fear that Britain will have to fall back on World Trade Organisation trading rules as it crashes out of the single market and customs union.
ADS - which represents Britain's aerospace, defence, security and space sectors - earlier this week warned that "no deal is the worst outcome for the UK" and that a fresh approach to Brexit is needed following the General Election result.
Mr Parmley, who will speak alongside Chancellor Philip Hammond and Bank of England Governor Mark Carney at Mansion House, is also expected to emphasise the importance of immigration for UK business.
"One thing made clear is that this great, global City thrives on attracting and exporting international talent and capital.
"We surely all recognise that UK immigration policy should enhance our future workforce - enabling industry to fill specialist roles, build links with academia, and share staff and knowledge around the world."
Financial services, hospitality, farming and manufacturing trade bodies have all warned of calamity if the Tories follow through on a so-called hard Brexit, which would put hundreds of thousands of British jobs at risk.
"It is in everyone's interests that UK financial services remain strong and competitive," Mr Parmley is expected to say.
"This sector's voice is of paramount importance. In order to protect its ability to create jobs and growth across the nation. To protect the 2.2 million-strong workforce in UK financial and related professional services. And to protect those with whom they work.
"And in the wake of the General Election, the Cities of Westminster and London have a shared duty, to work together, to minimise uncertainty and maximise calm."