According to the recruitment firm, 8,568 positions became vacant in July - 16 per cent down on the same month the previous year.
This also represents the seventh straight month of declines, as credit crunch-hit banks look to cut their workforces.
In a separate poll conducted by Morgan McKinley, which is owned by Imprint, three out of four bosses claimed that it is now more difficult to hire new employees than it was a year before.
Two thirds also said that they expect salary growth to remain flat over the months to come, due to the financial pressures currently being faced by firms.
The average City worker's annual pay was found to have reached just under $100,000 last month.
Commenting, chief executive at Imprint Robert Thesiger said: "Considerable levels of uncertainty remain within the financial services industry and in turn, the recruitment market."