Rail minister Tom Harris said that Britain did not need faster trains that would consume more energy but should instead focus on reducing congestion and reliability on the existing network.
"The argument that high speed rail is a green option does not necessarily stand up to close inspection," said Harris, in a letter to Liberal Democrat MEP Chris Davies.
"Increasing the maximum speed from 200km/h to 350km/h leads to a 90% increase in energy consumption. In exchange, it cuts station-to-station journey times by less than 25% and door-to-door journey times by even less."
Harris' claim was rubbished by Campaign for Better Transport executive director Stephen Joseph.
"I think the claim about increased energy consumption is oversold," he told NCE. "It's based on a study made some time ago on a theoretical level."