Mayor of London Boris Johnson believes the aborted strike on London Underground was broken by commuter power.
RMT say "the ball is in management's court" while London Underground claim "the ball is now firmly in the RMT leadership's court".
The fight broke out as the train approached Aldgate East station on Monday night, hours after the Tube strike began.
RMT accepts invitation to ACAS on Friday. @itvlondon
- London Underground says 52% of Tube services are operating today
- Around 80% of stations are open, more than yesterday
- Around 90% of the usual number of Oyster cards were used on overall TfL network this morning
The two sides in the tube strike expected to return to ACAS on Friday. @itvlondon
TfL says all tube lines open including for the first time on a strike day the Waterloo & City. @itvlondon
There are more transport problems in the capital because of fog this morning.
TfL suspended ferry services on the Thames because of poor visibility, saying Thames Clipper tickets were being accepted on local buses and Docklands Light Railway.
London City Airport in Docklands also reported delays to flights due to poor visibility.
The RMT has this morning accused tube bosses of allowing stations to become "dangerously overcrowded" during the second say of strikes.
Members of the Rail, Maritime and Transport union will end a 48-hour walkout at 9pm tonight, with a further, three-day stoppage planned for next week.
LU said half of train services ran yesterday and two-thirds of Tube stations were open, much more than during a previous strike in February.
Nearly 90% of the usual number of Oyster cards were used on Transport for London's network, according to the company.
But there was still huge disruption to travel, long delays for Tubes and big queues for buses.