The treaty to sell uranium to India will face tough scrutiny after the former chief atomic watchdog warned the deal lacked safeguards to ensure Australia did not inadvertently fuel India's nuclear bombs.

The treaties committee of Parliament must endorse the deal, signed by Prime Minister Tony Abbott in September, before uranium exports can start.

But John Carlson, the former chief of Australia's nuclear safeguards organisation, has told the committee India's nuclear weapons program is expanding and has complex links to civilian reactors.

The warning is likely to rattle Labor's lukewarm support for sales, the party having opposed uranium exports to India initially and scotched a Howard-era proposal.

Labor's position was reversed in 2011 after a push by former prime minister Julia Gillard and the promise of strict safeguards.