UK Foreign Secretary Liz Truss has vowed to clamp down on "unfair protests" after a small group of climate activists disrupted her speech at a Tory leadership hustings in East Sussex.

The five protesters, believed to be from the Green New Deal Rising group, heckled Ms Truss over climate change and energy bills.

They could be heard shouting "shame on you" and calling for a Green New Deal.

Ms Truss described them as "infiltrators", before vowing to clamp down on "militant trade unions" and "unfair protests".

"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," Ms Truss said after they left the studio.

"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."

She added that she will "make sure that militant activists such as Extinction Rebellion are not able to disrupt ordinary people who work hard and do the right thing and go into work".

"I will never ever, ever allow our democracy to be disrupted by unfair protests," Ms Truss said.

UK Foreign Secretary Liz Truss

The disruption came as Ms Truss was in the middle of delivering her opening speech at the fourth of 12 official Conservative leadership hustings.

Another protester was later escorted out as Ms Truss was in the middle of a question and answer session with Tory members.

"I take it as a compliment that I'm so popular with Extinction Rebellion," she said.

Her bid to become UK Prime Minister got a major boost after Conservative former minister Nus Ghani came out in support of her campaign at the beginning of the debate.

Ms Truss was introduced by Ms Ghani, who told Tory members that because of her role as the vice-chairwoman of the 1922 Committee of backbench Conservative MPs, she had not been able to back a candidate until this stage of the race.

The former chancellor Rishi Sunak was instead introduced by Deputy Prime Minister and Justice Secretary Dominic Raab, who told members Mr Sunak is the best candidate to "beat Keir Starmer and to win the next election".