Sloper was returned unopposed as Member of Parliament for Great Bedwyn at the 1715 general election.
He was defeated at the poll at Great Bedwyn at the 1727 general election, but was returned on petition on 26 March 1729.
He did not stand at the 1741 general election but was brought in as MP for Whitchurch, Hampshire at a by-election on 2 January 1742.
His son and heir William was also an MP for Great Bedwyn and was involved in a notorious affair with the actress Susannah Maria Cibber.
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