The Rail Regulator Tom Winsor has written to the infrastructure company saying an attempt to stretch its commitment to meet a shortfall on its passenger delay targets from one year to two was "completely unacceptable".
Mr Winsor, who took over the post three weeks ago, accused the rail giant of reneging on commitments given on performance levels drawn up by the company itself.
"I remind you that these published targets are Railtrack's own targets," he wrote. "I also remind you that as late as January this year you confirmed your commitment to those targets.
"It cannot be right that an important public commitment of that nature by a regulated company should be subjected to amendment or withdrawal at the discretion of the company."
Railtrack had promised to cut the number of minutes of delay per train by 7.5 per cent a year for the next two years but only managed a reduction of 2 per cent for the last year.
Earlier this year, the Office of the Rail Regulator demanded that Railtrack make up the shortfall within 12 months. The company responded by offering to do so within three years.
A reply from the rail watchdog that this was unsatisfactory was met by an offer from Railtrack to make good the deficit "as soon as possible" with a commitment to complete the task within a maximum of two years.
This was today met with an unequivocal response from Mr Winsor, who has informed Railtrack he was passing a copy of his letter to the Deputy Prime Minister John Prescott.
Mr Winsor said: "I have now reviewed all the papers relating to this subject and concluded that your proposal is completely unacceptable."
Among the options open to Mr Winsor will be punitive action against Railtrack. He added: "I will write to you shortly when I have made my decision on next steps."
Railtrack later said it was "disappointed" at the failure to meet its performance target and pledged to rectify the shortfall.
A spokeswoman added: "Improving performance remains Railtrack's key priority. We were disappointed in the figures last year and we are committed to making up as much as possible the shortfall in passenger train delays this year."Reuse content