A proposed ban on drinking alcohol on trains and buses is "another example of the Labour nanny state", say the government's political rivals.
24-hour drinking will soon be legal, but maybe not on the bus or train
Ministers said the move was designed to protect people from drunken yobs, and no decision had been made.
The Tories said the plan, which would also stop people having a drink with meals, was "completely over the top".
They and the Lib Dems said it was absurd to ban drinking on trains and buses while letting pubs open 24 hours.
The proposed ban, which is unlikely to include flights, is thought to have some police backing.
But the Conservatives believe the proposal is linked to the imminent new licensing laws, to try to control the behaviour of people travelling between areas looking for a 24-hour pub.
Shadow culture secretary Theresa May said violence on public transport was caused by people drinking too much in pubs
She described the proposal as, "very surprising" and "another example of the Labour nanny state going completely over the top."
Meanwhile the Liberal Democrats said the plans were "contradictory and confused".
And, after the row over the smoking ban, Lib Dem home affairs spokesman Mark Oaten said: "This government seems obsessed with banning things.
'Rights and responsibilities'
"This is rarely a clever solution to social problems and penalises responsible, law-abiding citizens.
"With each passing day, we are getting closer and closer to living in a nanny state."
A Home Office spokesman said no decision had been made on the public transport drink ban, but Defence Secretary John Reid admitted "it is a proposal for discussion".
Cabinet minister John Reid said government policies were based on a "balance of rights and responsibilities".
"It is right that people should be able to have a civilised drink at whatever time they want, but it is right also that people should be responsible about not being abusive on buses and other places," he told the BBC.
The Home Office would not comment on any leaked documents, but a spokesman said: "As part of the 'Respect Agenda' we are considering a whole range of proposals."
"Nothing has been ruled in or out at this stage."
A paper outlining the government's scheme would be published in December, he added.
The Association of Train Operating Companies said some companies already ban alcohol on their trains as part of their conditions of carriage.