HS2 could cost up to £22billion more than its previous budget and may be delayed, according to the Government.
The high-speed railway - which is designed to link London to the north - is planned to run through large parts of Derbyshire.
Construction of the Derbyshire section of the route, called Phase 2b, had been expected to start in the mid-2020s with the line through the county starting to carry passengers around 2033.
On Tuesday, Transport Secretary Grant Shapps told Parliament that Phase 2b was now expected to open between 2035 and 2040.
He added that the previous budget for HS2 was £55.7b but it could cost up to £78b, with both figures at 2015 prices.
Commenting on the news, Sir John Peace, chair of Midlands Connect and Midlands Engine, said: "HS2 is the best way to add the extra rail capacity we so desperately need to rebalance our country's economy.
"In the Midlands and the North, we are backing HS2 in full, stand ready to build it in full, and are impatient to start benefiting from it in full."
Opponents, however, say the scheme is too expensive and environmentally damaging.
Last month, the Government announced it was launching a review into HS2.
The 'independent and vigorous' review by retired engineer Douglas Oakervee will consider whether the major project should still go ahead - or if changes need to be made to elements of the scheme.