Cabinet Office Minister Francis Maude insisted there are "definitely more" government cuts to come on top of the £5 billion in "efficiency savings" set out for the first year of the next parliament.
The Tory MP said the Government had already saved £10 billion over the last year from "unglamorous" areas like job cuts and renegotiating services but suggested there was still plenty of room to root out unnecessary spending across Whitehall.
Mr Maude admitted some of the ways cash would be clawed back, such as halting civil service automatic pay progression, were "not without their controversy".
He told Murnaghan on Sky News: "There's more to come. Frankly, even if it was the most efficient organisation in the world there would be more to come.
"The best organisations find efficiency savings every single year because that's just what you do. The best companies do this every year so there's definitely more to come and we are nowhere near the most efficient organisation in the world.
"Last year alone, the year to March, we took out £10 billion of efficiency savings. This is from the unglamorous part of running an organisation - it's getting out of properties we don't need to be in, it's by reducing our headcount, it's by renegotiating contracts with our biggest suppliers, it's by moving services online so they are being done in a way that's convenient for the citizen, for the user of the service as well as being much, much cheaper for the taxpayer."
The £5 billion of fresh efficiency savings account for nearly half of the £11.5bn in total savings set out by Chancellor George Osborne in the 2015/16 spending round last Wednesday.