Claire Coutinho has been appointed as the UK's net zero minister, after Grant Shapps was named as the new Minister of Defence.
Ms Coutinho, 38, is the first woman and second person to hold the position, which was created by Prime Minister Rishi Sunak in a mini cabinet reshuffle this year.
Her remit as Secretary of State for Energy Security and Net Zero will include overseeing Britain’s efforts to reach its goal of net zero by 2050.
The appointment comes weeks after Mr Shapps announced Britain will host a global summit on energy security with a major focus on net zero early next year.
He said the gathering should include major oil companies and representatives from the UAE, Saudi Arabia, Qatar and other Middle Eastern nations.
The international conference is part of Mr Sunak's attempt to boost Britain's standing on the world stage.
Ms Coutinho’s promotion comes three months before the UK is expected to send a delegation to Cop28 in Dubai.
She previously served as minister for children, families and well-being, a position David Johnston will now take on.
Labour’s shadow climate and net zero secretary Ed Miliband criticised the successive turnover of ministers in the energy portfolio.
He posted on X, formerly Twitter, saying the Conservatives’ approach means Britain will not receive the energy policy it needs.
“I congratulate Claire Coutinho on her appointment as Energy Secretary,” the former Labour leader said.
“But it speaks volumes about the failures of Tory policy that we are now on to the sixth secretary of state since 2019.
“Reshuffling of the deckchairs will not deliver the proper energy policy Britain needs.”
Mr Miliband accused Mr Shapps of damaging the UK’s energy security.
“The new Energy Secretary needs to recognise that Grant Shapps’ approach has been a disaster and distance the government from it,” he said.
“Shapps’ opposition to clean, homegrown power has damaged Britain’s energy security, and his attempt to have a culture war has alarmed businesses.”
In a speech at the Institute for Government’s Net-Zero Conference in central London in July, Mr Miliband said Britain is sorely lacking in public investment in green energy initiatives.
Jess Ralston, an energy analyst at the Energy and Climate Intelligence Unit, a UK-based non-profit organisation, said there will be a lot of urgent tasks awaiting Ms Coutinho.
“Energy efficiency schemes that have delivered bill savings for homes in the past are flatlining and the government’s delay to insulation standards in the private rented sector will see renters, who are also voters, facing higher energy bills in the years to come,” Ms Ralston said.
She said Mr Sunak’s administration is dragging it heels on energy commitments.
“Energy security has never been a higher priority, and insulating homes, moving away from gas boilers and building more British renewables all help make us less vulnerable to global oil and gas markets,” she said.
“It's a no-brainer to focus on these net-zero policies to ensure households are shielded from future market volatility, getting on with delivering them will surely be a priority."
Ms Coutinho's new role was announced by Downing Street shortly after Mr Shapps was named Secretary of Defence, following Ben Wallace’s resignation.
Grant Shapps named British defence secretary - in pictures
Mr Shapps said he was “honoured to be appointed as defence secretary by Rishi Sunak.”
“I’d like to pay tribute to the enormous contribution Ben Wallace has made to UK defence and global security over the last four years,” he wrote on X.
In July, Mr Wallace announced his intention to stand down as an MP at the next election and said he would bow out of his defence role at the next cabinet reshuffle.
After failing to secure the top post of Nato general secretary, he appears to have had enough of frontline politics.
Mr Shapps has an extensive portfolio in politics but has never before held a position in the Ministry of Defence.
Unlike his predecessor, he does not come from a military background.
Mr Shapps is a cabinet veteran having held five positions in the past year alone. He was first appointed to a cabinet role in 2010 when David Cameron, who was prime minister at the time, asked him to be housing secretary.
In the past 12 months, Mr Shapps has served as transport secretary under Boris Johnson, had a brief stint as home secretary under Liz Truss and was made business and energy secretary after Mr Sunak took office.
This role was refashioned into energy security and net-zero secretary during Mr Sunak’s mini reshuffle of his top team in February.