Network Rail has admitted that it will miss key cost savings targets on its £4bn track-replacement programme in the body's current five-year plan.
The state-backed owner of most of Britain's track and biggest stations, was tasked with being 20 per cent more efficient with money spent on renewals to 2014, known as Control Period 4 (CP4).
Track renewals involve replacing battered sections of railway tracks.
In a recent board meeting, Network Rail directors concluded that track renewals "remain a major concern" and that the "target for the last year of CP4 was ambitious and it is likely that these targets will not be met".
This could mean the Office of Rail Regulation will demand even tougher efficiency targets in the next control period, having already ruled Network Rail's estimate that it needed to spend £40.1m over those five years to 2019 was £2.2bn too much.
In a statement to The Independent on Sunday, Network Rail added: "Over CP4 we're predicting to have invested in track renewals just shy of £4bn with targets of 20 per cent efficiency and we're currently looking at around 12-14 per cent. Our take on this is that with increasingly better understanding over the period on the condition of our assets we have needed to move our priorities for our work for more focus on the main line where expensive, main-line track renewals makes up almost 50 per cent of our work, rather than the 15 per cent predicted at the beginning of the control period."
The meeting also highlighted its tensions with Virgin Rail, noting one decision taken against the wishes of Sir Richard Branson's empire on the West Coast Mainline franchise was "politically very difficult".