New York could be the winner of Brexit, London warns EU and UK leaders

Several of the City of London's most prominent voices have warned leaders of the European Union (EU) and the U.K. that New York is set to be the winner from Brexit unless they avoid mutually destructive negotiations over the future of the U.K.'s financial sector.

The message, which has been repeated throughout the week, served as a thinly veiled warning to EU leaders that unless they co-operate with the U.K. in working towards the least damaging outcome for Brexit, the trading bloc also stands to lose significantly, rather than be well-positioned to benefit from the potential loss of U.K.-based firms' so-called passporting rights.

The sharpening of rhetoric can be seen as an attempt to position the EU and the U.K. on the same team as Brexit negotiations proceed, rather than as enemies on opposite sides of the table.

It comes on the back of antagonistic messages from leaders, such as EU Council President Donald Tusk, who said last week the only options facing the U.K. were a "hard Brexit" or "no Brexit" and European Commission President Jean-Claude Juncker who affirmed the EU would be "intransigent" in its dealings with Britain.

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The sun sets on Lower Manhattan and One World Trade Center in New York City on October 6, 2016 as seen Hoboken, NJ.

At a Thursday night banquet for City business leaders, London Mayor Sadiq Khan and City of London Corporation Chairman Mark Boleat took the microphone to lay out in stark terms the threat to financial sector jobs in the U.K. capital posed by challenger cities abroad, such as New York, Singapore and Hong Kong.

According to Boleat, "It is already apparent that the biggest beneficiary of any job losses in the U.K. will be New York, and some employment will simply stop as the volume of business can no longer be supported by the higher costs."

In his view, a third of jobs lost in the City could move to New York alone, with an equal amount being dispersed among European cities and a final third simply evaporating.

Sadiq Khan's speech revealed his frustration that appeals to the U.K. government to focus its concerted efforts on avoiding an acrimonious withdrawal from the EU seemed to be "falling on deaf ears".

Turning to the continent, he asserted, "Hard Brexit really is a zero-sum game for Europe."

Earlier on Thursday, while speaking exclusively to CNBC at his Mansion House residence, Lord Mayor Jeffrey Mountevans, whose main role is to represent, support and promote the City of London, shared a parallel view.

"What I'm hearing most is the danger is that perhaps business would go to New York," he said.

Beyond viewing Brexit as an opportunity to snap up business, the Lord Mayor also advised consideration of the potential downside for EU enterprises of a diminished London, saying, "We feel it is important for European businesses to have the expert guidance and advice and servicing capability that the City of London provides."

A study of the Global Leading Financial Centers published last month showed London just hanging on to its number one position with New York only one point behind - this on a scale that runs to 1,000 points.

The strong desire for resetting the tone to create a constructive dialogue as details of the U.K.'s departure from the EU are thrashed out was summarized by the Lord Mayor when he told CNBC, "We are very anxious to retain good links with Europe."

He also echoed Khan's warning that the detriment of pursuing a hard Brexit would be felt much more widely than the City.

"Not only would it not be for London it wouldn't be good for Europe," he concluded.

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