Morgan replaces deputy leader Daisy Cooper who moves to become the party's Treasury spokesperson.
The MP, who was elected to the North Shropshire constituency in 2021, has been spokesperson for housing, communities and local government since 5 July.
Her appointment comes after Lib Dem MP Layla Moran was elected as chair of the Health and Social Care Committee.
Lib Dem leader Ed Davey, said: ‘I am humbled by the result of the General Election and the millions of voters who put their trust in the Liberal Democrats, including many for the first time.
‘We will stand up for our communities every day on the issues that matter most, fixing health and care services, tackling the cost of living crisis and protecting our precious environment.'