The work and pensions secretary has insisted her planned overhaul to benefits rules will be fair, as Labour MPs wait for details of expected welfare cuts.
Liz Kendall said the plans, to be published on Tuesday, would put rising benefits expenditure on a "sustainable footing".
The government insists changes are required to reduce ballooning spending on health benefits, which are predicted to continue rising in the coming years.
But the move has faced opposition with Labour ranks, and has already led charities to warn of the potential impact on vulnerable claimants.
Ministers have already abandoned plans for a one-year freeze to PIP payments, after disquiet from MPs.