The Tories say access to health and education in developing countries must be guaranteed
The Tories are "investigating" whether aid vouchers could be used to let people in poor countries shop around for the best schools and services.
The Observer reported that plans for the vouchers and to spend £9.1bn overseas aid on funding for private schools were in a leaked document.
Frontbencher Andrew Mitchell said they were "ready to work with the public, private and not-for-profit sectors".
But minister Mike Foster said the idea was "unworkable and ideological".
The Observer reported the plans were contained in a Tory policy document leaked ahead of the government's white paper on development this week.
The proposals suggest vouchers "would be redeemable for development services of any kind with an aid agency or supplier of their choice".
Mr Mitchell, the Conservatives' international development spokesman, said: "Governments have a responsibility to guarantee access to health and education for everyone, particularly the poorest.
"We stand ready to work with public, private and not-for-profit sectors to help make that happen. I don't have any ideological hang-ups about whether it's private provision or public provision - I'm interested in what works."
But International Development minister Mr Foster said the voucher plan looked "unworkable and ideological".
He said: "Following the revelation on the ConservativeHome website that 96% of Tory candidates think the aid budget should be cut, this new plan looks like an attempt to placate Tories who are not committed to the UN aid target of 0.7%."
Conservative leader David Cameron has promised to match Labour's plans to increase development spending to 0.7% of GDP by 2013.