Labour has not given up on high speed rail but wants to ensure that "costs are kept in check", a source from the party has told Associated Press.
"What we have always said is that we have got to manage these costs properly, we can't let these costs spiral out of control," said the source.
"What we need to look at is how those costs have got out of control and whether it is the best way to spend £50 billion."
"We have been pretty clear and consistent that we support the principle of a North-South rail link," he said. "There is backing for the project, but not backing for this project without regard for cost or with a blank cheque."
The Prime Minister says the money to pay for HS2 will need to come from 'a balance' between the Government and 'the train user' - but expensive tickets are necessary for 'Britain to be a success'. See the full interview above.