Liz Truss was heckled by protesters shouting "shame on you" during a speech at a Tory hustings.
The Conservative leadership hopeful was on stage at the event in Eastbourne when shouting could be heard in the audience.
Young activists, believed to be from the Green New Deal Rising Group, heckled Ms Truss over climate change and energy bills.
One protester, Fatima Ibrahim, shouted: “Shame on you!”
As she was bundled out, allies elsewhere in the Winter Garden theatre joined the stunt as activists shouted: “Out! Out! Out!”
Ms Truss said: "I think we have some infiltrators and I will wait until they are evicted."
Tory members in the audience booed as five protesters were led away, shouting "shame on you", calling for a "Green New Deal" and claiming to be the majority.
Ms Truss told party members she would crackdown on disruptive protests.
She said: "Can I just say a few words on the militant people who try and disrupt our country and who try and disrupt our democratic process and try and disrupt our essential services.
"I would legislate immediately to make sure that we are standing up to militant trade unions who stop ordinary commuters getting into work. And I would legislate to protect our essential services."
The Foreign Secretary was later heckled again as she tried to take audience questions, with another protester being escorted out.
She quipped: "I take it as a compliment that I'm so popular with Extinction Rebellion."
Activist Ms Ibrahim said later: “This is a critical moment for our country.
“Our next Prime Minister should be responding to what the majority wants, which is good wages, secure jobs and a safe climate.
“But Liz Truss and Rishi Sunak are clogging up the airwaves with policies that will make things worse, not better.”
The wannabe PMs both faced the grilling after both made missteps this week as the race for No10 becomes increasingly fractious.
Leaked footage emerged today of Mr Sunak bragging to Tory members that he had worked to divert funding from "deprived urban areas" towards more prosperous towns.
Speaking ahead of the hustings, the former chancellor defended his comments, saying he was making the point that "deprivation exists right across our country".
It comes after Ms Truss was forced into a screeching U-turn over a plan for regional pay boards which aimed to pay public sector workers less if they lived in poorer areas.
Labour's Rachel Reeves said the pair were showing their "true colours".
She said: "First Liz Truss says she’ll cut the pay of public sector workers outside London, now Rishi Sunak is boasting he fixed the rules to give taxpayers’ money to rich Tory shires.
"This leadership race is revealing the Tories’ true colours. Britain needs a fresh start with Labour."
Meanwhile, Ms Truss' bid to become PM was given a boost after Conservative former minister Nus Ghani came out in support of her campaign at the start of the hustings.
Mr Sunak was introduced by Deputy PM Dominic Raab, who told members Mr Sunak is the best candidate to "beat Keir Starmer and to win the next election".
