The trend for organisations to outsource major IT projects to management consultants such as Accenture, IBM and EDS has pushed up demand from consultancies for skilled IT staff, and driven up rates of pay, said Atsco.
Permanent IT staff in consultancies can expect to earn an average of £44,000 a year, compared to an average of £36,000 for those in financial services.
Freelance rates average £50 an hour in consultancies, compared to £43 in financial services, Atsco found.
"Talented IT professionals used to view the City as the source of the best jobs, but with big-ticket projects increasingly being outsourced, the high-paying work is often now with consultancies," said Atsco chief executive Ann Swain.
The biggest pay differentials are between consultancy staff working on public sector projects and those working in the private sector.
Compared to the big bucks on offer in the consultancies, permanent IT staff in the public sector earn an average of £25,000 a year, and contractors £38 an hour.
Financial services companies are expected to outsource more major IT project work to consulting organisations over the next 12 months, fuelling further demand for skilled IT staff, said Atsco.
The demands and pressures on IT departments have grown as they embark on more bespoke projects, making outsourcing more attractive, said Swain.
"When a bank begins a major IT project from scratch, it is often reinventing the wheel. A consultancy is likely to have far greater experience in that area and is usually prepared to carry the can if things go wrong. It often reduces risk if you bring in a team with a proven track record."
The UK outsourcing market is forecast to grow to 24% of the total IT services market this year, up from 15% in 2002, according to Ovum Holway. This will mean it is worth a total of £10.5bn.
However, some financial services organisations have bucked the trend by taking IT projects back in-house. JP Morgan recently announced it would be cancelling a £2.8bn outsourcing contract with IBM.