New Energy Secretary Ed Davey will seek to establish his green credentials on Monday, declaring there will be "no change in direction or ambition" after the departure of Chris Huhne.
In a concerted effort to reassure environmental groups and Liberal Democrat activists, Deputy Prime Minister Nick Clegg will join him on a visit to bolster the message.
Huhne, who earned a reputation as a fierce defender of the Government's climate change priorities, resigned on Friday to fight charges of perverting the course of justice.
The promotion of Davey from a role as a business minister raised fears among some campaigners that the agenda might lose out to Treasury cuts under his command.
A note of caution was also sounded by former Lib Dem leader Sir Menzies Campbell against any watering down of commitments on a policy area of "iconic" importance to the party.
And the scale of the challenge facing Davey was underlined by the revelation that 101 Tory MPs had written to the Prime Minister calling for a cut in taxpayer subsidies to onshore wind farms.
Davey, who a spokesman pointed out had campaigned on environmental issues since he was a student, will begin his first full day in the job meeting graduates looking to take green jobs.
"I have long believed in the need to marry our economic and environmental agendas," he will say.
"Greening the economy isn't just good for the planet, it's good for the wallets, purses and pockets of every British citizen too. My priorities are very simple: green jobs, green growth and getting the best deal for energy bill payers.
"My department is already implementing bold and ambitious reforms - like electricity market reform and the Green Deal - to unlock private investment, drive innovation and build a resilient, green, competitive economy. It's now my job to see those through.
"There may have been a change at the helm, but there'll be no change in direction or ambition."
Clegg, who was due to join Mr Davey at a testing facility for green homes near Watford, will warn the UK must "wake up, or end up playing catch up" with emerging economies.
"In today's world the savviest states understand that going for growth means going green. Low-carbon markets are the next frontier in the battle for global pre-eminence," he will say.
"We have every reason to be confident: the combination of enviable wind, wave and tidal power, a world-beating research base and a proud history of engineering give the UK a clear competitive edge. So we're already in pole position. But the reality is we need to sharpen our elbows if we want to stay ahead.
"I want the UK to be the number one destination for green investment. We're in this race to win."
Davey also marked his first day by announcing the 155 community projects that have succeeded with bids for a £5.1 million pot from the Local Energy Assessment Fund.