Broken Tube rails 'have tripled'

Hand-held detectors are used to test the rails

The number of broken rails on the Tube network has trebled over the last five years, according to a report leaked to BBC London.

In the document London Underground (LU) said the number of rail breaks, which rose from 18 in 2000 to 55 last year, was "unacceptably high".

The latest report on improvements to the network showed less than 10% of track had been replaced.

However David Waboso, of LU, said a "huge amount" was being replaced.

Multiple breaks

He said that "in some cases the programme is slipping but we are working... to recover the programme and we will continue to monitor it very closely".

There have been multiple rail breaks around Farringdon, Seven Sisters, Baker Street, Clapham South and Notting Hill Gate in the last five years.

Engineers use hand-held detectors to check the rails once a year.

Responsibility for repairs passed to two infrastructure companies in 2003.

Tube Lines and Metronet received 30-year contracts worth £15bn under the Public Private Partnership scheme.

Earlier this year a LU report showed work by these companies to be behind schedule.

BBC London transport correspondent Andrew Winstanley said London Underground had more than 500 miles of track but the last official report showed only 30 miles had been replaced - well behind target.