Commuters can expect fewer late trains, if NR reaches it targets
Network Rail (NR) has been ordered to increase efficiency while getting by on less money than it asked for.
The Office of Rail Regulation said the infrastructure firm will have just under £27bn to spend in the next five years - £2.4bn less than it wanted.
NR has been told it needs to cater for more freight and passengers, as well as deliver major projects like Thameslink.
The company said it was "considering" the settlement's implications.
The regulator ruled that NR will need £26.7bn between 2009-2014 - 8% less than the £29.1bn NR requested.
In return, NR has been given a target of increasing its trains-on-time figures to 93% on the busiest routes in south-east England - a 3% improvement on current figures.
Elsewhere, the target has been set at 92%.
Office of Rail Regulation (ORR) chief executive Bill Emery told the BBC that he expected NR to improve its overall efficiency by a fifth over the next five years.
He said he expected the company to cater for a 20% increase in passenger numbers and a 30% increase in railway freight.
The regulator has also given the green light to a number of major railway projects - including the Thameslink route that connects north and south London, the rebuilding of Birmingham New Street station and a new line to Glasgow airport.
Mr Emery said: "NR has delivered significant improvements to reliability, asset condition and efficiency over the last five years, against the backdrop of strong passenger and freight growth.
"Our determination provides the funding necessary for NR to build on this to deliver further improvements for train operators, passengers and freight customers and expand capacity for the long term benefit of the railway."
'Up its game'
Despite the funding announcement, rail passengers will have to contend with continuing - although hopefully less-disruptive - weekend engineering work for many years to come.
NR fell foul of the ORR earlier this year following disruptive new year engineering overruns - the worst of which was at Rugby, Warwickshire, on the London to Scotland West Coast Main Line. It led to NR being fined a record £14m by the ORR.
Gerry Doherty, leader of the TSSA rail union, described the funding announcement as "tinkering at the edges".
He said: "Improving punctuality targets is important but it will be meaningless if NR merely timetables longer journey times as it has done in the past to meet those targets. Trains running up 10 minutes late are already said to be on time.
Big rail projects to come
Connecting King's Cross commuter services into the Thameslink route
Rebuilding Reading and Birmingham New Street stations
Improving line speeds on the Midland Main line
New Glasgow Airport rail link and a new line from Airdrie to Bathgate
Extensions to more than 500 platforms to accommodate longer trains
"This will not tackle our fundamental problem - that we run the most expensive and overcrowded network in Europe."
Mr Doherty added that problems would not be solved by making passengers pay more or "dithering over whether to build a new high-speed line to relieve chronic overcrowding".
Shadow transport secretary Theresa Villiers said: "NR needs to up its game on efficiency and value for money if it is going to deliver the new capacity that passengers are crying out for."
She added: "But Labour must also deliver on the promises it has made on tackling chronic levels of overcrowding on the rail network - a problem they have been far too slow to wake up to."
And Liberal Democrat transport spokesman Norman Baker said it is essential that savings come from better management practices and greater efficiency, not by cutting back on schemes that increase railway capacity.
He added: "Unless we have a serious programme to reopen closed railway lines, increase capacity and build new stations, travellers will not escape cattle-truck Britain."