The Chancellor must abandon planned cuts to pension tax relief for high earners in the emergency Budget, the National Association of Pension Funds says.
The trade body said Labour's moves to restrict tax relief on pension contributions for people earning more than £150,000 would hit far more workers than originally estimated.
It urged George Osborne to take the opportunity to scrap the policy - set out in the Finance Act 2010 - on Tuesday.
NAPF chief executive Joanne Segars (pictured) said: "In particular, we urge them to rethink the recent changes to pensions tax relief. The move would ensnare many others beyond the high earners being targeted and would weaken the approach to workplace pensions."
The NAPF predicted the proposals will cost between £2.5bn to £3bn to implement and lead to senior corporate decision-makers disengaging from workplace pensions, eroding employer interest in the schemes.
It suggested reducing the amount of pension contribution eligible for tax relief from £255,000 to about £50,000, which will limit the tax relief available to high earners, but in a way less harmful to pension provision.
"Our alternative will be less damaging to pension saving and cost far less to implement," Segars said.
The NAPF is also calling for greater issuance of long-dated and index-linked gilts to help pension schemes manage the risks of pension provision.
Segars said: "This is a win-win-win solution for employers, pension schemes and the government. Skewing issuance towards longer maturities would provide the government with a cheap and secure source of finance at a time of exceptionally large public sector deficits."
The submission also outlined seven principles that could help bring objectivity to the debate on public sector pensions.
Segars said the key to addressing "pensions apartheid" was to raise the level and vision in the private sector, rather than lower public sector provision.
