Environment minister Zac Goldsmith has defended his appointment to the unelected Lords after losing his Commons seat in the election last month.
Lord Goldsmith lost his Conservative Richmond Park seat to the Liberal Democrats on December 12.
His appointment to the Lords came after Nicky Morgan controversially kept her Cabinet post as Culture Secretary.
Ms Morgan stood down as an MP before the election, but was then made a life peer, allowing her to return to the Cabinet.
In his maiden speech from the despatch box, Lord Goldsmith of Richmond Park said: "I know my appointment to this House wasn't everyone's cup of tea.
"One political rival described me as a 'turd that won't flush' - a phrase my children are very unlikely to let me forget.
"But equally I know many of those heroic people engaged in the battle to protect this extraordinary planet and the species it holds are cheered by having another voice in Parliament and it is an enormous privilege."
In a debate on fishing policy, the former MP said he had been given a "surprisingly warm welcome" in the Lords but he would miss working directly for his former constituents.
Lord Goldsmith told peers the environment had preoccupied him for as long as he could remember, and dominated his work in the Commons, adding: "I'm enormously grateful that I'm able to continue doing so full time as part of a government that has made tackling these issues a top priority."
He said the damage that humans were doing to the planet was "self-evidently" the most important issue for politicians to tackle.
The appointment of Lord Goldsmith and Culture Secretary Nicky Morgan to the Lords prompted Labour claims of cronyism and "jobs for mates" of the Prime Minister.