Reports that planning delays are threatening the roll-out of air-conditioned Tube trains have been denied by Transport for London (TfL).
Westminster Council has deferred plans for an electricity substation amid concerns it would "look out of place".
TfL said suggestions this would delay the new fleet were "utter nonsense".
TfL said the trains will be introduced on the Metropolitan Line in September 2010 and then rolled out on the Circle, Hammersmith & City and District lines.
Under the plans, the power station would be built near Edgware Road Tube station.
Engineering trials are already under way for the first fleet of air conditioned Tube trains.
Cllr Michael Brahams, Westminster's planning applications sub committee chairman said: "There is no reason why TfL cannot ensure the infrastructure needed to support these improvements does not have an adverse effect on local residents or look out of place.
"We have deferred this application so that TfL can work with our planners to find a resolution as quickly as possible as we are anxious to help them improve the Tube."
But a TfL spokesman said reports in the press that delays threaten the new fleet were "utter nonsense".
"We are confident that by working closely with Westminster council we can soon progress this," he said.
"In any case, these planning issues will not prevent us from introducing the first of the new S-Stock trains next year, as promised."
Revised plans are expected to be heard by Westminster Council by the end of August.