Labour's leadership has been defeated after the party's conference voted to back rail renationalisation.
Darling says money should not be turned away
Labour's high command has blamed the defeat on union block voting, saying local constituency parties voted to keep the railways in private hands.
But renationalisation is not thought likely to become Labour policy, despite the 63% vote for it at conference.
Chancellor Gordon Brown effectively ruled out such a move on Monday, claiming it would cost £22bn.
The card vote on renationalisation came at the end of a debate on the issue on Monday, when a show of hands was too close to call.
Chancellor Gordon Brown, in a speech earlier on Monday, ruled out renationalisation, arguing it would cost £22bn.
Speaking on Newsnight, BBC political correspondent Martha Kearney said the leadership may have lost a vote, but she had been told that renationalisation was very unlikely become party or government policy.
"They say it's something they definitely won't be doing," she added.
She said that the leadership would justify their stance by saying that, although the unions voted overwhelmingly for the motion, constituency parties voted against it.
Tony Blair and Mr Brown were united in firmly opposing the renationalisation, which they consider a huge waste of government money, she added.
In Monday's debate, Transport Secretary Alistair Darling urged delegates not to back renationalisation, saying private companies were investing £70m a week in the rail network and it was senseless to lose that cash.
But union leaders insisted it will not cost extra money.
The general secretary of the Transport Salaried Staff Association raged against the original Conservative privatisation of the railways.
Gerry Docherty told delegates they had the chance to "start the reversal of one of the most blatant, bare-faced robberies of the British people".
He paid tribute to extra government investment and said Britain's railways would be the envy of the world if it was all spent on the railways instead of some of it reaching private pockets.
"Your trains do not work," he said. "We are paying more money, vast amounts more, for a worse service to the private sector."
The scheme would not cost anything as train franchises would be taken back when current contracts expired, he added.
But Mr Darling said fragmentation between track and trains caused by the initial privatisation had been addressed.
And he said decades of chronic underinvestment in railways had to be reversed.