Julian Smith has been named as chief whip after Gavin Williamson, who previously held the post, was promoted to Defence Secretary by Theresa May.
The Skipton and Ripon MP, who was formerly Mr Williamson's deputy, will be responsible for enforcing party discipline and ensuring Tory MPs vote with the government - a vital job after Ms May lost her Commons majority in the general election.
Esther McVey, a former work and pensions minister in the coalition government, was made deputy chief whip.
The surprise reshuffle comes after Sir Michael Fallon became the first Cabinet casualty of the growing Westminster sexual harassment scandal, when he resigned from his role as Defence Secretary on Wednesday night.
In his resignation letter, Sir Michael said his conduct had "fallen below the high standards required" of the role and actions that might have been acceptable in the past were not acceptable now.
The ex-Defence Secretary admitted making unwanted advances on journalist Julia Hartley-Brewer at a party conference dinner in 2012, although the radio host said she found the incident "mildly amusing".
The new chief whip grew up in Stirling, in Scotland, and read English and History at the University of Birmingham before going on to work as an entrepreneur.
Mr Smith joined the whips office in 2015 and he was promoted to deputy chief whip by the Prime Minister after the general election.
