Pakenham, a veteran of the Peninsular war whose sister was married to the duke of Wellington, continued to sit for county Westmeath on the interest of his brother Thomas, 2nd earl of Longford, an Irish representative peer. Like Longford, who received a British peerage in 1821, he continued to support the Liverpool ministry, but he was a lax attender.
At the 1826 general election Pakenham, who had been elected for Westmeath on an anti-Catholic ticket, abandoned his seat amidst reports that he had been ‘discarded’ by his brother and the ‘high Protestant interest’, which he tried to deny. He was ‘the victim of the vote he gave ... in favour of emancipation’, declared the Catholic press.
