Tube travellers were stuck underground tonight after a power cut hit London.

London Underground said the power failure was having a "serious" impact on the whole of the network. Rail services from major stations including Victoria, London Bridge and Waterloo were also affected.

A Tube spokesman said: "There has been a National Grid failure which has affected the underground. At the moment we are assessing the impact of that but it is having a serious impact on the whole system at the moment."

He added: "It's also having an effect on some of our buildings. Certainly quite a lot of the network appears to be affected."

He said the failure happened around 6.15pm and there were likely to be a number of people stuck underground.

He added: "There will be travellers underground. I don't know the extent of that yet. It's at the end of rush hour, the peak period, so it's a busy time."

A spokesman for electricity network operator EDF Energy said: "We have lost supplies to large parts of south London in the last few minutes as a result of a National Grid failure supply in the south London area.

"It's difficult to predict how long this is going to take. National Grid has got to get the circuit back."

A spokesman for British Transport Police said the power cut had affected all major railway stations in south London.

"There is no power in a lot of stations and no trains running in the whole of south London," he said.