The Monster Employment Index shows the year-on-year drop to be the greatest it has recorded. In London vacancies online dropped for the 11th consecutive month mostly in engineering, HR, marketing, PR and media.
Of the occupational groups, managers and professionals saw the steepest falls in demand.
But Hugo Sellert, head of economic research at Monster, said: "Overall, online recruitment in the UK has fallen once again. There is cause for optimism, however, in some sectors. Hiring of education and production workers rose in March and healthcare has shown encouraging annual growth."
March shows biggest ever year-on-year drop in online recruitment
There was a further dip in online recruitment in March, following a slight increase in February, with online recruitment levels during March 41% lower than the same time in 2008 - and HR being one of the most affected professions.