Karyl Nairn and Ric Hawley, who own apartments directly opposite the proposed development, have filed an application in the Supreme Court that could cost more than $100,000.
The residents said their case relied on the fact that Town Planning Scheme No. 6 did not give the Metro Central Joint Development Assessment Panel (JDAP) power to approve a high-rise residential building on the peninsula.
The JDAP approved construction of the tower in late May, drawing the ire of residents groups and local politicians, some of whom described planning processes as a farce.
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READ NOWResidents had sent petitions to the State Government, attended public meetings with council and formed the Save the South Perth peninsula action group to oppose the plan.
Mill Point Road resident Vicki Redden said it was unfair that residents should have to take such drastic action.
"There are no third party appeal rights; the developer can go to State Administration Tribunal if they are rejected but the average person has no avenue other than the Supreme Court," Ms Redden said. "JDAP is supposed to offer expert advice and look at these proposals more closely.
"Nobody would have contemplated a 400 per cent over-compensation in size.
"Now we have two residents spending all this money to take the matter to court on behalf of other affected residents."