Conservative candidate for London mayor Zac Goldsmith has joined calls for the Government's tax credit cuts to be eased.
The Richmond Park MP said George Osborne's reforms were "necessary", but should be phased to protect people on low incomes.
"Taxpayers shouldn't be subsidising low pay so these reforms are necessary," he told The Sun.
"But I am pressing Government to phase them so the lowest paid are protected - and to make sure any losses are absorbed by higher wages."
The comments - which echo concerns voiced by current Mayor of London Boris Johnson at the Conservative Party conference - come ahead of a Commons debate next week on Labour's demand for the changes to be scrapped.
Although the result is not binding on ministers, any rebellion by increasingly nervous Tory backbenchers would be highly embarrassing.
Work and Pensions Select Committee chairman Frank Field has also been urging more action to offset the impact on the poorest households and could draw cross-party support.