STRIKES by London Underground workers could be escalated in the New Year with walkouts lasting up to three days considered, union leaders have warned.

But officials of the Rail Maritime and Transport (RMT) union and the Transport Salaried Staffs' Association (TSSA) said they would not be recommending any walkouts over the festive season.

The move appeared to rule out any more strikes before January 10, giving a respite to travellers in London.

It came as Tube services were disrupted today, Monday, by a 24-hour walkout in protest against job losses.

Bob Crow, general secretary of the RMT, said: "We are moving towards an escalation of the action in the New Year. I don't think it will be appropriate to have action over Christmas."

Mr Crow said his executive will consider the next move later this week, adding this could lead to two or three-day strikes or action in an entire week by different groups of Tube workers.

"I will not be recommending any action this side of January 2, but come 2011 we will have to consider escalating strikes to more than one day."

Earlier, Transport for London was accused by Mr Crow of "misleading" travellers over the impact of a strike by thousands of Tube workers which has disrupted services for the fourth time in recent months.

The company said Tube services were running on nearly all lines, although adding that "some stations may be currently closed".

The RMT said the walkout had had the greatest impact yet, claiming that "ghost" trains were running as a "PR stunt".

Thousands of members of the RMT and the Transport Salaried Staffs' Association walked out at 6.30pm on Sunday in protest at 800 ticket office job cuts.

Mr Crow said: "Once again RMT and TSSA members have stood rock solid in this dispute over Tube safety.

"TfL and LU have been reduced to their usual well-rehearsed lies over services that they claim are running but it is pure fantasy and simply misleads Londoners. The capital is locked down across the board."

TfL said: "Tube services are running on nearly all lines, despite a strike on London Underground called by the leaderships of the RMT and TSSA unions.

"The Northern line is running a service across the full length of the line, and the majority of the Victoria, Jubilee, District lines are also being served."

Mike Brown, managing director of London Underground, said: "Services are operating on virtually all lines this morning despite the pointless strike.

"We are doing everything we can to get as many Tube services as possible operating, and to keep Londoners on the move with extra buses, river services, and other alternatives. Londoners will face some disruption, but we intend to continue to run services on nearly all Tube lines, meaning that people will be able to get around."

The 24-hour walkout began at 6.30pm Sunday. cuts.

It is the fourth strike in recent months in a dispute over a long-running dispute over 800 ticket office job following the collapse last week of talks aimed at breaking the deadlock.

Transport for London (TfL) pledged to run as many Tube services as possible, although it warned services would not return to normal until Tuesday.

The RMT said there was severe disruption on the Jubilee Line due to signal failure at Westminster and station closures due to the immediate impact of the strike.

"The District, Hammersmith and City and Victoria Lines are already severely disrupted due to the immediate impact of strike action. The impact of the action has kicked in earlier than on previous strikes as RMT and TSSA members remain rock solid," said an RMT spokesman.

Mike Brown, London Underground's managing director, accused the unions of being "cynical" and pledged to do everything possible to keep London moving during the latest strike. Writing on his blog, which went live on LU's intranet, he said the behaviour of the unions this week and during the current dispute "brings into question the motivation of some of those who claim their role is to protect their members".

"This looks extremely cynical to me - the unions say they are concerned about safety; well, let's take six weeks and sit down and look at each of these concerns. Instead, the union leaderships would rather have their members out on strike - a strike that they know is pointless," he said.

RMT general secretary Bob Crow said: "It is incredible that LU management would not agree to a 12-week suspension of the cuts to allow a thorough safety evaluation on the impact on each station of their cuts plans. That shows complete and utter contempt for the safety of both their passengers and their staff. With more chaos as a result of infrastructure failures, adding to a month of misery, Londoners can see the real impact of the LU/TfL cuts plans for themselves and it is those very same safety-critical cuts that are at the heart of this dispute."

Nick Winch, of the Federation of Small Businesses, said up to two-thirds of staff were late arriving for work or couldn't get in at all during the last strike earlier this month, costing businesses up to £3,000.

Transport for London said: "We'll run as many Tube services as we can, but some lines will have a restricted service and some stations will be closed."