The move was backed by Karin Svensson Smith, head of transport police within the Greens, who pushed for "a functional national operator that takes complete control".
"And you don't get that when other foreign competitors come in and just skim the cream off the profitable lines," she told the Dagens Nyheter newspaper (DN).
Foreign companies like Hong Kong based MTR are competing for the fastest trains between Gothenburg and Stockholm, the biggest earner on Swedish railways, while commuters and freight trains suffer slower journeys.
"If we give SJ a reasonable task, then we can demand that they maintain traffic on the other lines," she continued.
However Social Democrats MP Anders Ygeman, who sits on the parliamentary committee on transit, admitted that deregulation hasn't been perfect, but pointed out it has had some positive effects.
He was nevertheless cautiously optimistic toward the idea of exploring the idea of reinstating SJ's monopoly status.
"We could consider trying the method of letting one operator, for example SJ, having responsibility for a whole stretch, from trains, tracks, to stations," he told DN.
"We're keen to see the full picture, and are prepared to start over."