High court's refusal to take up the case means that an appeals court decision striking down the controversial law will stand

Attempts by conservative states to restrict abortion rights in the US suffered another legal defeat on Monday after the Supreme Court refused to hear an appeal from pro-life politicians in Arizona that could have threatened parts of its famous Roe v Wade ruling.

Pro-choice groups welcomed the decision which they said was an important reassertion of the principle that the constitution protects a woman's right to choose regardless of laws passed by states.

The state of Arizona sought to have its appeal heard by the supreme court after lower courts ruled that a new law banning abortion after 20 weeks on the grounds that it caused pain to the foetus was unconstitutional.

However, the supreme court declined to hear the appeal on Monday, effectively upholding the decision of the ninth circuit court of appeal, which covers Arizona. No further explanation for the decision was offered by the justices, but it is the latest in a string of legal setbacks for states looking to tighten abortion rules and pro-choice groups heralded it as an important victory.

“The supreme court soundly declined to review the ninthcircuit’s sound decision that Arizona’s abortion ban is clearly unconstitutional under long-standing precedent,” said Nancy Northup, President and CEO of the Center for Reproductive Rights, which helped bring the original legal challenge. “This ensures that no Arizona women’s lives or health are harmed by this callous and unconstitutional law.”

In December, the federal appeals court for the seventh circuit also affirmed a lower court decision to block a law in Wisconsin imposing a restrictive requirement that doctors who provide abortion must obtain hospital admitting privileges.

But campaigners say the flurry of new anti-abortion legislation in conservative states continues to pose a threat to reproductive rights. “Today the court did the right thing, but women’s health is still on the docket — not only at the supreme court, but in active cases all across the country,” said Cecile Richards, President of Planned Parenthood Federation of America on Monday.

“This unprecedented assault against women’s constitutional rights shows it’s time for new leaders who value women’s health. A dangerous and blatantly unconstitutional law like Arizona’s abortion ban should have never passed in the first place.”

In bringing the case, Arizona's attorney general had sought to argue that banning abortion after 20 weeks rather than the 24 weeks when a foetus is normally deemed viable was a regulation of the law upheld 41 years ago under Roe v Wade rather than challenge to it.

Governor Jan Brewer signed the ban into law in April 2012. Nine other states have enacted similar bans starting at 20 weeks or even earlier.

Nevertheless, pro-life groups may fare better in the Supreme Court on Wednesday in another case where it has decided to hear an appeal against buffer zones created outside abortion clinics to keep protestors away from visiting patients.

The case, McCullen v Coakley, will hear arguments that a ruling in 2000 unfairly restricts the free speech of protestors.