2013 incomes show the Big Six still dominate public IT contracts.
The Government spent £4.3bn with the traditional big six IT firms last year, according to think tank Institute for Government.
Here's who they are and how much they earned.
HP - £1.7bn
Hewlett Packard pulled in £1.7bn in each of the last two years to become the largest single recipient of Government money, according to the report.
But a think tank spokesman warned the figures were being reexamined after the Government disputed them.
The researchers initially believed 86% of HP's public sector revenue came from a job centre contract with the Department for Work and Pensions (DWP), but the DWP told CBR the figure was "just wrong".
A spokesman added: "The correct figure is several hundred million a year to cover the majority of IT services and IT development used by DWP.
"This includes the IT platforms which are used for the processing of benefits and pensions."
Capgemini - £1.01bn
The French IT services firm also counted £997m from public sector contracts in 2012, found the think tank.
Source: Company Press Release