A federal judge has blocked part of the extremely restrictive Texas anti-abortion law that attracted national attention after state senator Wendy Davis held an 11-hour filibuster to block it in June.

In what was a partial victory for Planned Parenthood, one of the largest women's health providers in the US, the judge ruled that a key provision of bill HB2, a requirement for abortion providers to have admitting privileges at a local hospital, was unconstitutional.

Last month Planned Parenthood brought a lawsuit challenging two of the key provisions in the bill, HB2, after it was passed by special session in the state following Davis's successful filibuster against it. The bill required physicians performing abortions to have admitting privileges at a hospital within 30 miles of a clinic. Such privileges are very difficult for abortion providers to obtain, and the effect would have been to shut down abortion providers in the state.

A second clause, to limit abortion-inducing drugs, was also challenged by Planned Parenthood, but allowed by the judge to stand.

The ruling, issued on Monday by US District Judge Lee Yeakel, struck down the admitting privileges provision. The judge ruled that such a provision is "without a rational basis" that it places an undue burden on a woman seeking an abortion, and therefore was unconstitutional.

The judge ruled that the provision on restricting medicated abortions do not place such an obstacle in the way of a woman seeking an abortion, except when a physician determines an abortion is necessary for the preservation of the life or the health of the mother.

Texas had argued that when an abortion provider has admitting privileges they are more likely to effectively manage complications by provide continuity of care and thus decrease medical errors.

However, Yeakel ruled that a lack of admitting privileges on the part of an abortion provider is of "no consequence" when a patient presents at an emergency room, that it does nothing to further the interest of patient care through communication, nor does it impact timelines.

"The court concludes that there is no rational relationship between improved patent outcomes and hospital admitting privileges within 30 miles" of an abortion facility, the ruling said.

However it noted that, if the provision were introduced, evidence is that abortion clinics will close, and that 24 counties in the Rio Grande Valley would be left with no abortion provider.

Women's healthcare providers and others who brought the suit said the provision the judge blocked would have made safe and legal abortion unavailable for a third of Texas women. In a statement shortly after the ruling, the Center for Reproductive Rights said: "Today's decision has averted a catastrophic health crisis for women across the state of Texas."

Nancy Northup, president and CEO of the CRR, said: "Politicians, not doctors, pushed for both of these unconstitutional restrictions – despite the best medical standards for women's health care."

Cecile Richards, President of Planned Parenthood Federation of America, said: "Today's ruling marks an important victory for Texas women and sends a clear message to lawmakers: it is unconstitutional for politicians to pass laws that take personal, private decisions away from women and their doctors."

The provisions of HB2 ruled on on Monday were part of a package of legislation signed by Governor Rick Perry on 18 July following a series of special legislative sessions,

The groups said that, by upholding the law's restriction on medicated abortions, physicians in Texas would be forced to require their patients to follow an outdated and less effective protocol for medicated abortion.

Courts across the country have opposed similar measures requiring admitting privileges for abortion providers in state laws as unconstitutional. Similar admitting privileges requirements have been halted before they took effect in Alabama, Mississippi, North Dakota and Wisconsin. State courts in North Dakota and Oklahoma have permanently struck down unconstitutional restrictions on medication abortion.