Washington - US President Barack Obama on Monday reversed an eight-year long government block on federal funding for embryonic stem cell research, a promising but controversial science, and rejected what he called a "false choice" between science and morals.

Obama signed an executive order that overturned former president George W Bush's policy limiting research on the cells, which was put in place during his first year in office back in 2001. Fulfilling a 2008 campaign promise, Obama said his administration would "vigorously support" scientists who pursue stem cell research.

In a separate memorandum, Obama directed government agencies to restore "scientific integrity" to their decision making in another implicit attack on the Bush era, which critics said put political ideology over science.

Obama's actions marked the latest shift in government policy on hot-button ethical issues. Obama last month reversed Bush's ban on funding for international family planning organizations that perform abortions.

Proponents of embryonic stem cell research believe the method could lead to cures of a variety of diseases, including Parkinsons and cancer. But religious conservatives consider the destruction of human embryos involved in the process to be immoral.

Bush had restricted the use of government money to research on existing colonies of stem cells and barred the use of such money on new colonies.

"While such research is unfortunately legal, taxpayers should not have to foot the bill for experiments that require the destruction of human life," said Tony Perkins, president of the Family Research Council.

Perkins urged Obama to seek "common ground" by focussing on more ethical methods such as using adult stem cells. Supporters of the science argue both avenues should be open to research.

Obama said the promise of embryonic stem cells "should not be overstated" and said he respected the objections of religious groups. But he argued the ethical pitfalls were not as deep as the debate would suggest.

"In recent years, when it comes to stem cell research, rather than furthering discovery, our government has forced what I believe is a false choice between sound science and moral values," Obama said.

Obama also slammed the Bush administration for ignoring science when it conflicted with administration policy on issues such as climate change.

Obama directed his top science advisor in the White House to put together a strategy for "restoring scientific integrity to government decision making" in all federal agencies.

"It is about ensuring that scientific data is never distorted or concealed to serve a political agenda and that we make scientific decisions based on facts, not ideology," he said.

The Bush administration was long viewed as skeptical of the science behind climate change. Obama by contrast supports mandatory controls on the carbon-dioxide emissions blamed for warming the earth.

Obama last month reversed another Bush-era policy that limited the input of government scientists on construction projects that could harm endangered species.