Job openings in England's financial sector dropped over 10% following the Brexit vote, as concerns over UK passporting and access to the single market hit the jobs market.
Fresh data released by the Institute for Public Policy Research (IPPR) shows that financial sector vacancies fell 10.1% across England, decreasing in every region in July and August.
"This is striking as it is the only year in the past four where this trend has occurred," IPPR said.
London saw a 13.6% drop in job adverts, including for administrators, managers and chief executives, it said.
Outside the capital, job postings saw a 12.8% drop in the North East, an 11.4% fall in the North West and an 11.2% drop in Yorkshire and the Humber.
IPPR's research, carried out with Burning Glass, follows reports by recruiter Morgan McKinley which showed that financial sector job vacancies slumped 12% in July, but expanded 4% in August.
It prompted the recruiter to warn that uncertainty around the UK's Brexit negotiations was still "casting a shadow over the second half of 2016".
IPPR is now calling on the Government to secure passport rights in a bid to restore confidence in the financial sector.
Clare McNeil, IPPR associate director for work and families, said: "This new data shows the immediate impact that the vote to leave the European Union appears to be having on the finance sector.
"As one of our largest sectors, the financial sector is vital to the wider wellbeing of our economy.
"The Prime Minister needs to end doubts around whether the Government will pursue access to the single market and passporting rights as high priorities in the Brexit negotiations."
The UK's financial watchdog earlier this week disclosed that 5,476 UK firms hold a total of 336,421 passports, which provide access to the European Union's single market in financial services.