Rachel Gilmour, MP for Tiverton and Minehead, will take a seat on the Public Accounts Committee.
It is tasked with scrutinising public expenditure and ensuring the efficient running of public services.
Ms Gilmour, a former civil servant with the Environment Agency, will bring her understanding of responsible and transparent handling of taxpayer money to the role.
This experience, along with her insights into local government spending decisions from her time as chair of the scrutiny committee at Mid Devon District Council, will guide her.
She said: "I’m delighted to join the Public Accounts Committee to help oversee the UK's finances.
"My Lib Dem colleagues and I will ensure value for money, champion public services, and scrutinise those working on behalf of the public.
"I’m committed to playing my part for Tiverton and Minehead, and all who put their trust in the Liberal Democrats."
The Public Accounts Committee meets twice a week and holds the government and civil servants accountable for the delivery of public services.
Ms Gilmour's appointment comes at a time when strong, experienced voices are crucial on this committee.
She looks forward to holding the government to account for the people of Tiverton and Minehead, and the UK.
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