Zac Goldsmith is not fit to hold any government position.
Prime Minister Boris Johnson has drawn opposition fire for letting defeated ex-Tory MP Zac Goldsmith - formally owner and editor of The Ecologist - keep his ministerial post by making him a life peer.
Liberal Democrat Sarah Olney, who took the minister's Richmond Park Commons seat in last week's general election, said the move made a mockery of Mr Johnson's claim to lead a "people's government".
The move comes after Nicky Morgan, who stood down as an MP at the election, kept her Cabinet post as Culture Secretary as she was made a life peer.
Ms Olney said: "Along with the appointment of Nicky Morgan, we are seeing Boris Johnson now making a mockery of his so called 'people's government'.
"It is the first days of Parliament returning and already Boris Johnson is rewarding his cronies with peerages."
Labour's shadow culture minister Jon Trickett said the minister, who was defeated in the London mayor race by Sadiq Khan in 2016, was not fit to hold a Government position.
Mr Trickett said: "It says everything you need to know about Boris Johnson's respect for democracy that he has ignored the voters of Richmond Park and appointed Goldsmith to Government.
"The public deserve better than a government appointed by 'jobs for mates'. At a time when the Conservatives are investigating racism in their party, they've appointed the person who ran an overtly racist campaign against Sadiq Khan.
"Zac Goldsmith is not fit to hold any government position."
Downing Street said: "The Rt Hon Zac Goldsmith has been confirmed as a Minister of State (unpaid) at the Department for the Environment, Food and Rural Affairs and the Department for International Development.
"The Queen has been pleased to signify Her intention of conferring a peerage of the United Kingdom for Life on Zac Goldsmith."
The Richmond Park seat was held by Ms Olney for six months between December 2016 and June 2017 when the Tory triggered a by-election after resigning to fight Heathrow expansion as an independent candidate.
The 44-year-old had held the seat for the Tories since 2010, securing a majority of 23,000 in 2015, but lost to his Lib Dem rival by 18,638 to 20,510 after the party fought a successful anti-Brexit campaign.
The scion of the eponymous banking dynasty clawed back the constituency by the thinnest of margins, just 45 votes, in the snap election of 2017 after returning to the Conservative fold.
The 2017 result was finally called at around 7am after multiple recounts.
He was rewarded for his change of heart with the position of environment minister in Boris Johnson's government.
But the staunchly pro-Brexit minister was always an awkward fit in a constituency that voted 72 percent Remain in the EU referendum.
At the December 2019 election, Ms Olney polled 34,559 votes compared to the Tory's 26,793 on a turnout of 79 percent of the electorate.
Shaun Connolly and Harriet Line are both PA political staff.