An impassioned teen survivor of the deadly Florida shooting has become the new face of gun reform, with her angry cry of “We call BS” galvanising supporters around the world.

Emma Gonzalez, 18, who escaped injury during the Marjory Stoneman Douglas high school massacre last week, gave a fiery 12-minute speech to a crowd of thousands outside the Fort Lauderdale federal courthouse on Sunday.

Through tears, the student – who lost 17 classmates and teachers in the shooting – ridiculed President Donald Trump and other politicians for sending “thoughts and prayers” without delivering gun reform.

“To every politician taking donations from the NRA, shame on you!” she thundered. The crowd echoed her chant.

“If the President wants to come up to me and tell me to my face that it was a terrible tragedy and … how nothing is going to be done about it, I’m going to happily ask him how much money he received from the National Rifle Association.”

As is typical of the President when commenting on mass shootings by white suspects, Mr Trump heavily praised the police and ambulance officers who attended the shooting, expressed sympathies for the victims and pledged to “tackle the difficult issue of mental health”. He largely avoided commenting on gun laws.

On Sunday, he criticised the FBI – which is investigating alleged collusion with Russia by his campaign staff – for failing to prevent the shooting.

“Very sad that the FBI missed all of the many signals sent out by the Florida school shooter. This is not acceptable,” Mr Trump wrote on Twitter.

“They are spending too much time trying to prove Russian collusion with the Trump campaign – there is no collusion. Get back to the basics and make us all proud!”

Ms Gonzalez has garnered worldwide attention for her impassioned speech to a rally of students, parents and local residents. Photo: Getty

In her speech, Ms Gonzalez criticised how easy it was to buy a gun, and hit back at false claims that the students had failed to warn authorities of the alleged shooter’s violent tendencies.

“We certainly do not understand why it should be harder to make plans with friends on weekends than to buy an automatic or semi-automatic weapon in Florida,” she said, to loud applause.

Nikolas Cruz, 19, an expelled student, has been charged with 17 counts of premeditated murder. The AR-15 rifle he allegedly used was purchased legally in Florida.

It is not unusual for mass shootings to prompt backlash against lax gun laws in the US. The difference this time is that the movement is being led by a new generation of millennials – whose views on guns differ from their parents and grandparents.

Fourteen of the 17 victims. Not pictured are Peter Wang, 17, Helena Ramsay, 17 and Alexander Schachter, 14. Photo: CBS News

Speeches at the rally by Ms Gonzalez and other teen survivors have garnered huge support on social media, raising hopes of reform.

“We are going to be the last mass shooting,” Ms Gonzalez told the crowd.

“We are going to change the law. That’s going to be Marjory Stoneman Douglas in that textbook, and it’s all going to be due to the tireless efforts of the school board, the faculty members, the family members and most importantly the students.”

Polls by the Pew Research Centre have shown that support for gun control has quite consistently sat above 50 per cent for Americans aged 18-29 for the past 20 years. This level of support has been consistently higher – often by several percentage points – than any other age group.

Donald Trump is often photographed with local law enforcement after mass shootings, as he did in Florida. Photo: Getty

Other students at Marjory Stoneman Douglas have sparred with gun-rights activists on social media, given many television interviews and spoken at vigils that doubled as rallies for safer gun laws.

However, past movements have failed, despite seemingly strong electoral support. Pew research showed that all age groups except 50-64 supported gun control after the Columbine shooting in 1999, with 18-29 year olds peaking at just over 75 per cent (compared to 58 per cent last year).

And yet, little progress was made.