Danny Alexander has said sleep was the "last thing on his mind" as he juggles his workload at the Treasury and helping out with his two-week-old baby.
The Highlands MP was appointed chief secretary to the Treasury following the resignation of David Laws.
Mr Alexander told the BBC News Channel he was up for the "enormous" challenge that came with the role.
He said his new role and looking after a young family meant sleeping was last in his thoughts.
The MP for Inverness, Nairn, Badenoch and Strathspey has two daughters with his wife.
He was among the Liberal Democrat MPs who negotiated with the Conservatives on forming a coalition government.
Appointed Scottish secretary, he was moved to the role of chief secretary at the end of last month.
Mr Alexander told the BBC News Channel: "It is an enormous challenge but it is a challenge that I am very much up for.
"I think that having led the negotiations for the coalition agreement for the Liberal Democrats and then having worked through the full agreement over the subsequent week, I think that I have the judgement and expertise that is necessary to do the job effectively."
Asked in the interview if he will have time for much sleep, he added: "With a combination of an imminent budget, a spending review to follow and a two-week-old daughter at home I think sleep is the last thing on my mind."
Mr Alexander more than doubled his majority at the general election.