Later London Underground service being considered
Plans to run the Tube later on Friday and Saturday nights are being considered by London Underground.
Mike Brown, managing director of London Underground (LU), said later running was being "looked at" now that progress was being made in modernising the Tube.
Changes would not come into effect until 2015 at the earliest.
The RMT union's head criticised Tube officials for "spinning ideas" without speaking to their staff.
Mr Brown said: "This is not imminent and we still have much work to do, but I recognise the importance to London.
"There is clearly a balance to be struck between extending our hours of operation, which would mean less time to do upgrade work, and the understandable desire for a later running Tube."
At the moment the Tube runs from about 05:00 GMT and closes shortly after 01:00.
It ran an hour later during the London Olympics.
But Tube bosses were criticised by Bob Crow, general secretary of the transport union RMT.
He said: "It would be nice if senior Tube officials had the decency to talk to their staff and their unions within existing agreements before they start spinning ideas out about extending hours and changing procedures."
He said changes to operational hours would mean major changes to rosters and require the recruitment of more staff, plus changes to maintenance and engineering work.
"None of that has been discussed with the unions in any forum and RMT does not conduct its negotiations via the media."
In 2010, Mayor of London Boris Johnson put plans to increase weekend opening hours until 01:30 on hold because of the Tube upgrade plan.
A Transport for London poll in 2005 showed 73% of Londoners were in favour of later opening.
Under the long-running Tube engineering scheme, on some nights up to 5,000 people are at work on the Underground, said Transport for London.