LGBT+ advocates filed a lawsuit on Tuesday to block a rule the US government said will allow medical professionals to act according to their consciences, but that critics said could deny care to those in need.

Under the more than 400-page rule written by the US Department of Health and Human Services (HHS), hospitals and doctors' offices must certify they 

are protecting employee consciences and religious rights or lose federal funding.

The so-called "conscience rule," which could take effect as early as July, permits health workers to opt out of procedures such as abortions and ­sterilizations which violate their beliefs.

The rule also opens the door to denial of care for LGBT+ patients seeking surgical transitions or hormone treatment, Jamie Gliksberg, an attorney with LGBT+ rights group Lambda Legal told the Thomson Reuters Foundation.

"When patients cannot be out to providers about their sexual orientation or gender identity, out of fear of being ­refused treatment, their mental and physical health is critically compromised," Gliksberg said.

She added that fear of discrimination can prevent patients from seeking out the prophylactic care they need, or cause them to wait to seek treatment until their needs are acute.

Civil rights lawyers also echoed advocate concerns that the broad language in the rule could lead to outright ­discrimination of LGBT+ patients, regardless of the kind of treatment they seek.

Genevieve Scott, a senior staff attorney for the Center for Reproductive Rights, said healthcare facilities could be intimidated into ending reproductive care and LGBT+ services altogether for fear of losing government funding.

Scott said it offers few limits on who makes those decisions, calling it "intentionally vague and unclear."

In response to the lawsuit, HHS pointed to the lengthy process the department had gone through in creating the rule.

"HHS finalized the conscience rule after more than a year of careful consideration and after analyzing over 242,000 public comments," said Roger Severino, director of the Office for Civil Rights at HHS in an emailed statement.

"We will defend the rule vigorously."

Lambda Legal was joined in the suit by the Center for Reproductive Rights, Americans United for Separation of Church and State and Santa Clara ­County, California.