Former prime minister Paul Keating has warned Labor’s plan to double the tax on retirement savings over $3 million could turn superannuation into a low- and middle-income pension scheme and damage community confidence in the $3.9 trillion savings system he created.

In private talks over the past month, Mr Keating has told industry super executives and union leaders that the government’s refusal to index the $3 million threshold to increases in inflation is “unconscionable”, according to people familiar with the discussions who spoke on the condition of anonymity.