Parts of the West Coast Main Line are closed for nine days

Delays for which it answered fell from 14.7 million to 13.7 million minutes in the year to 31 March, it said.

Track renewals were at a level "not seen for decades", with the lowest number of broken rails ever, it added.

The Rail Passengers Council said the improvements had come at the price of disruption. Much of the West Coast Main Line is currently closed for works.

The massive task of rebuilding our railways inevitably means that, at times, sections of the network have to be closed down Network Rail deputy chief executive Iain Coucher

In its report on network performance over the year to 31 March, Network Rail said delays in the last six months of the year dropped by almost 20% compared with the same period a year before.

It had renewed 853 miles of track - a rise of 36% compared with the previous year.

The number of broken rails - the problem that caused the Hatfield crash in October 2000 - fell by 25% to a record low of 334.

It had also renewed 380 points during the same period - a rise of 55% on the previous year.

It said more than 85% of trains ran on time in April 2003 - the best month since August 2000.

Delays were tumbling in the half of the network where it had implemented last year's decision to bring all track maintenance in-house, the not-for-profit successor to Railtrack added.

"Bringing maintenance in-house is really making a difference for passengers," a spokeswoman said.

Deputy chief executive Iain Coucher said much remained to be done to improve the network's performance.

"The massive task of rebuilding our railways inevitably means that, at times, sections of the network have to be closed down," he said.

"We're undertaking unprecedented levels of activity out on the ground, renewing tired and worn out infrastructure that has been starved of steady investment for many years.

We are still quite a long way from having a truly punctual railway Rail Passengers Council chair Stewart Francis

"Our ongoing success in reducing delays shows we are delivering a real return on this investment."

The Rail Passengers Council's Mr Francis said Network Rail had made "undoubted progress", but at the cost of substantial disruption to passengers.

"Performance is still far below the levels that passengers require to have certainty on all their journeys," he said.

"We are still not back to the levels of performance of pre-2000.

"We want 90% punctuality as soon as possible. We are still quite a long way from having a truly punctual railway."