A TTC “relief’’ subway line, a 20-year-old concept that died in the late 1980s, was resurrected this week at Toronto council amid heightened sensitivities over the future of mass transit in the region.

Councillors voted 31-13 to ask Metrolinx to give a higher priority in its 15-year plan to the downtown relief line — a subway or underground light rail that would run south from Pape or Donlands station to link directly to Union Station, and potentially continue west and north to Dundas West or Keele station.

The line is included in Metrolinx’s regional transportation plan, but on a hazy horizon of 25 years.

Toronto now wants it put ahead of the $2.4-billion plan to extend the Yonge line to Richmond Hill.

Mary-Frances Turner, vice­-­president of the York Re­gion Rapid Transit Corp., was cool to any idea of revisiting the long-term plan.

“We’d want (Metrolinx) to be very careful about that kind of significant change to a plan that was two years in the making.”

But Toronto councillor and former TTC commissioner Michael Thompson says Metrolinx should revisit its plans because Toronto’s system is bursting at the seams, with riders sometimes waiting four downtown trains to get on.

“What’s going to happen to the system in the downtown core? No one is dealing with that,” he said.