Transport Secretary Chris Grayling has said it is "incredible, inconceivable and simply nonsense" to suggest the cost of HS2 is set to spiral.
Mr Grayling told MPs that reports over the weekend were based on speculation from people not involved in the flagship high-speed rail project.
He also blamed his late appearance in the Commons on "cock-up not conspiracy", with MPs having earlier expressed anger that Mr Grayling had not appeared at the despatch box to confirm HS2's final routes to Leeds and Manchester.
Campaign group Stop HS2 said leaks from inside the project suggested the 351-mile line could end up costing in the region of £200 billion – nearly four times the current £55.7 billion budget.
In a statement to the Commons, Mr Grayling said: "There have been some wild rumours, I have to say, in the last 24 hours about the cost of the project, based on, frankly, a finger in the air by people who are not involved in the project.
"I would simply remind the House that it is incredible, inconceivable and simply nonsense to suggest that HS2 will cost five times the amount HS1 cost per mile.
"We have experience of major projects in this country.
"This project has a cost attached of £55.7 billion for the whole thing, it is currently on time and on budget and I expect it to stay that way.
"We've been pretty good with projects like Crossrail and the Olympics at delivering on time and on budget in this country, and I'm sure we will carry on doing so."
Monday saw three major announcements on the HS2 project.
Mr Grayling confirmed the decision on the route from Crewe to Manchester and Birmingham to the East Midlands and Leeds, as well as announcing the firms awarded £6.6 billion of contracts for building the first phase of the railway.
A Bill was also introduced in Parliament for the section from the West Midlands to Crewe, which will effectively act as a planning application.
Mr Grayling also sought to allay fears over Carillion, the troubled construction giant which is among those have been awarded contracts on HS2.
Speaking on Monday evening, he said: "We would all hope that it pulls through, because I want to see British business succeed, but what I would to say to him is Carillion are part of a consortium where the organisations involved have all committed to deliver their part of this contract.
"I have confidence that whatever the situation with Carillion, that consortium will deliver the results we expect."
Mr Grayling added that all companies would be obliged to leave a "lasting skills footprint" as a result of their work on HS2, through things such as apprenticeships.
Conservative Andrew Bridgen (North West Leicestershire) said he believed the project would cost an "awful lot more" than his own previous £100 billion figure.
He told Mr Grayling: "Do you share the concern of my constituents who absolutely expect that a Labour government would wilfully and neglectfully waste taxpayers' money but they despair now at seeing a Conservative government do exactly that on this project?"