US President Barack Obama has lifted curbs on federal funding for embryonic stem cell research, promising a ‘new frontier’ for US science free of political ideology.

The US president signed an executive order reversing the policy of predecessor George W Bush.

Critics say the ban on funding had hampered the fight into finding treatments for grave diseases such as Alzheimer's, Parkinson's and diabetes.

Warning that scientists were deserting the US for other nations, Mr Obama said ‘medical miracles’ come about only through painstaking research and rejected the ‘false choice’ between sound science and moral values.

‘When government fails to make these investments, opportunities are missed. Promising avenues go unexplored,’ he said at the White House, lauding the potential to help victims of debilitating illnesses and catastrophic injury.

‘Ultimately, I cannot guarantee that we will find the treatments and cures we seek. No president can promise that,’ Mr Obama said.

‘But I can promise that we will seek them - actively, responsibly, and with the urgency required to make up for lost ground,’ he said, paying tribute to advocates of the research such as late Superman actor Christopher Reeve.

‘Not just by opening up this new frontier of research today, but by supporting promising research of all kinds, including groundbreaking work to convert ordinary human cells into ones that resemble embryonic stem cells.’

Mr Obama directed the National Institutes of Health to formulate guidelines within 120 days on how to proceed with federal research on lines of stem cells procured from private laboratories such as fertility clinics.

His order cannot affect a congressional ban on federal money being used directly to create new stem cells, which are primitive cells from early-stage embryos capable of developing into almost every tissue of the body.

He vowed that he would not permit stem cell research to stray into the wilder bounds of science such as human cloning, which he said ‘has no place in our society, or any society.’

But there was still fierce fire from social conservatives and anti-abortion groups, who back research on cells taken from human adults rather than embryos.

House of Representatives Republican leader John Boehner said Mr Obama had undermined ‘protections for innocent life, further dividing our nation at a time when we need greater unity to tackle the challenges before us.’

Mr Bush barred federal funding from supporting work on new lines of stem cells derived from human embryos in 2001, allowing research only on a small number of embryonic stem cell lines that existed at the time.

The former US president argued that using human embryos for scientific research, which often involves their destruction, crossed a moral barrier and urged scientists to consider alternatives.