The makers behind a new movie about notorious abortion doctor Kermit Gosnell say Facebook blocked their attempts to promote it on the social media platform. 

Gosnell: The Trial of America's Biggest Serial Killer stars Dean Cain as a detective who investigates real-life abortionist Gosnell.  

Gosnell was the operator of an abortion clinic in West Philadelphia, where he was accused of performing illegal late-term abortions and terminating live births outside of the womb.  He was convicted in 2013 of first degree murder over the deaths of three babies at the clinic, and found guilty of involuntary manslaughter in the death of a woman during an abortion procedure there.

One of the producers of the movie, Phelim McAleer, said some supporters had tried to pay to 'boost' posts about the movie on Facebook without success.  

McAleer told The Federalist that the paid boosts had been rejected by Facebook without any explanation, but he accused the social media giant of having an anti-conservative bias - something Facebook CEO Mark Zuckerberg has previously denied.

'The Silicon establishment do not want this story told,' McAleer said.

'They [Facebook] simply state it's not been approved and to check their standards, but it does not give you a specific reason why this post could not be promoted at all to a wider audience.

'It's clear it is the pro-life audience that they don't want to encourage or provide content to. They really hate anyone who doesn't subscribe to the liberal world view.'

McAleer is worried that without Facebook as a marketing channel, many people will not even know about the movie. 

'As independent filmmakers, we have a limited budget and Facebook was a mainstay of our outreach efforts,' he said. 

The movie opened in 673 theaters on October 12 and has so far grossed over $2 million - nearly making back all of the $2.3m budget it raised through crowdfunding.

The report comes in the same week as a pro-life news site said its Twitter account was frozen for a day over a four-year-old post about an apparent link between unprotected homosexual sex and sexually transmitted diseases. 

LifeSiteNews said its Twitter account had been locked after Twitter administrators said the news site had violated its rules on 'hateful conduct'.

Twitter then unlocked the account and said in a message to LifeSiteNews that it had been locked in error. 

'We have restored your account, and we apologize for any inconvenience this may have caused,' the message to LifeSite Friday read.

'Twitter takes reports of violations of the Twitter Rules very seriously. After reviewing your account, it looks like we made an error.'

Despite the reversal by Twitter, Steve Jalsevac, co-founder and president of LifeSiteNews, also fears an anti-conservative bias in Silicon Valley.

'Twitter is now trying to force news agencies to report only what is acceptable to their personal, biased views and shutting down balanced, factual reporting on the homosexual issue,' he said.