Just over 35,000 posts were created in 2012, down 35% on the 54,025 a year earlier.
The study also showed around 800 City jobs were available in December 2012, compared with 1,490 in December 2011.
Astbury Marsden's chief operating officer Mark Cameron said: "2012 was a busy year for HR departments across the City as cost-cutting remained a key focus for senior management and board members throughout the year."
He added: "Tighter regulation including higher capital requirements forced up costs at a time when revenues dipped due to a number of factors including a continued weak economy and less trading activity.
"Although broad cost-cutting is fairly typical in the City during a downturn, 2012 was particularly significant as senior management in banks took very decisive action and implemented major structural changes including winding down entire units.
"Hopefully we are now behind the worst of the cost-cutting. Although banks may still tinker with staffing numbers, most of the obvious and immediate cuts are likely to have now been made."
There has been a spate of redundancies in the financial sector recently, as last month, banking giant Citigroup announced plans to axe 11,000 jobs worldwide - 4% of its workforce - to cut costs.
And in October, Switzerland's biggest bank UBS confirmed it was cutting 10,000 jobs to shrink its investment operations.
Of the total job cuts, it said 2,500 positions would be lost in Switzerland while the rest would be felt in the UK and US.
