The privatisation of the Tube has been a costly exercise not justified by its few added benefits, a report claims.
Metronet and Tube Lines took over Tube maintenance in 2003
The increase in safety incidents had "potential to become an increase in the number of accidents", according to the House of Commons Transport Committee.
It identified that a fragmented management system had led to "inconsistent communications" between privatised firms and their employees.
London Underground said the Tube is now safer and more reliable.
Metronet and Tube Lines took over responsibility for maintenance in 2003 following the introduction of the private-public partnership (PPP).
They signed 30-year contracts worth £15bn and combined profits of almost £100m.
Government funding for the Tube has risen enormously in recent years but increased investment and improvements could have been forthcoming without a PPP, the committee said.
Committee chairman Gwyneth Dunwoody said: "I welcome the fact that the government is at last putting real money into the Tube. But I cannot see why it needed a PPP to do it."
The committee said government spending on the Tube - disregarding the cost of the Jubilee Line extension - had risen more than twentyfold from £44.1m in 1997-98 to £1,048m in the current financial year.
Delays and cancellations
Bob Crow, of the Rail Maritime and Transport union, said the report "confirmed the PPP is an expensive scheme which puts guaranteed, risk-free profits into contractors' pockets despite their failure to deliver improvements."
Tube Lines said they were "disappointed" by the report which failed to recognise the progress made on day-to-day performance.
Metronet said performance in the second year of operation "demonstrates the development of a clear and positive trend".
In a statement London Underground said: "The Tube is improving. It is safer, cleaner and more reliable than it has been for many years, but we know there is much more to do."
The London Transport Users' Committee (LTUC), the watchdog representing transport users, said it had doubts about PPP and agreed with report's findings.
Brian Cooke, chair of LTUC, said: "If PPP is to work, the level of enhancement activity on the Underground needs to be dramatically increased so as to deliver the improvements that Londoners are entitled to expect."