Network Rail's (NR) net debt has risen to £25.74 billion, the rail infrastructure company announced today.
The figure - for the 12 months ending March 31 2011 - is an increase on the £25.05 billion figure for the previous 12 months.
But NR, which has no shareholders and is a not-for-dividend company, said its net debt remained "at an expected level".
The figure was released alongside NR's results for the period April-September 2011.
The figures showed:
:: Profit after taxation was £136 million compared with £275 million in April-September 2010;
:: Revenue was £2.99 billion compared with £2.87 billion;
:: Operating profit was £1.22 billion compared with £1.12 billion;
:: Capital expenditure - the amount invested in the railway over the period - was £2.07 billion compared with £1.73 billion.
In autumn 2008 NR was set the challenge by the Office of Rail Regulation of cutting costs by 22% between 2009 and 2014.
NR said today that by the end of last year an estimated 13% had been saved and in the last half-year efficiencies had contributed to further savings of more than £300 million.
NR predicted it would achieve more than £700 million of savings in this financial year. Total efficiency over the first three years of the 2009-14 period is forecast to reach between 16% and 17%.
A total of 92.8% of trains ran on time during the period April-September 2011 compared with 93.5% in the same period last year.
NR said punctuality has been adversely affected by increasing levels of cable theft on the railways which leads to signal problems.
NR's group finance director, Patrick Butcher, said: "We remain committed to running a safe railway with increasing cost efficiency, investment and performance.
"As we devolve responsibilities for much decision-making from the corporate centre to our routes, we will create a platform for new collaborative ways of working with our customers that will drive down the overall cost of the railway."