Transport company Stagecoach has urged the government to introduce tough new measures to tackle the increase in cable theft from the railways.
On Monday, services from Hampshire into London Waterloo were delayed after theft of cable near Guildford, Surrey.
And three separate incidents of cable theft last week disrupted services in and out of London Paddington and London Bridge and in Sussex.
The government said it was working with police and Network Rail on the problem.
Cable theft on the rail network grew by around a third between 2008/9 and 2010/11, despite a range of measures such as burying cables, use of CCTV, invisible marking of cable and a scrap dealer information programme in partnership with British Transport Police (BTP).
In June, cable thieves disabled the signalling system near Woking in Surrey, causing massive disruption for around 80,000 South West Trains passengers in the evening rush hour.
Bitter personal experience
Transport minister Norman Baker said the estimated cost to the UK from cable theft was £1bn, "and even that enormous figure doesn't take into account the loss of working hours caused by well over 16,000 hours of train delays".
Stagecoach chief executive Sir Brian Souter said: "Many rail customers know from bitter personal experience the terrible effect this can have on their daily lives.
"As well as the human cost of disruption, criminal activity in this area is now so damaging to our wider economy that we simply must act."
Mr Baker said: "Thefts like this cause misery for thousands of commuters and cause damage to the economy out of all proportion to the value of the cable itself.