David Williams, a local lecturer, fought the now marginal seat in west London at the general election. He has made clear his unhappiness that Labour's National Executive Committee did not even shortlist him this time round.
But as Gordon Brown, the Chancellor, stepped out alongside the new candidate in the constituency yesterday, the party was emphasising Mr Slaughter's "excellent" qualifications for the vacancy created by the death of the Tory Sir Michael Shersby. And Mr Brown was plugging all of his 10-week track record in office as a powerful vote-winner for the 36-year-old barrister at the poll on 31 July.
The Chancellor cited the new windfall tax spending on education and health, the cut in VAT on fuel and action for small businesses as reasons for ending 27 years of Conservative representation in the prosperous constituency. Speaking in the heart of small business - Zeus Metal Fabrications, which employ six people making metal machinery in Uxbridge - Mr Brown said they were taking nothing for granted. "We know that this is an uphill fight. But we're going to put to the people of Uxbridge our record of the last two months." Mr Slaughter said: "I am delighted to have been selected by Uxbridge Labour party members to fight this seat on behalf of Tony Blair's new Labour Party."
Playing down tales of local dissatisfaction at his candidature, Mr Slaughter emphasised his experience in modernising Hammersmith and Fulham council in west London, where he is leader. "I have helped to improve people's quality of life. I can do the same in Uxbridge."
He dismissed the Liberal Democrat candidate, Keith Kerr, a British Airways manager at Heathrow, as out of the running.
And he said: "The Conservatives under new leader William Hague are as much of a shambles as they ever were under John Major." But Lord Parkinson, the new Conservative Party chairman, gleefully picked on the selection row, claiming the decision to adopt Mr Slaughter demonstrated the "breathless arrogance" of Labour in government. He contrasted the Labour candidate with the Conservatives' John Randall, 42, the owner of a well-known Uxbridge department store founded by his great grandfather, Philip, in 1891.
"Labour had to show their candidate where Uxbridge was on the map. He has been parachuted in," Lord Parkinson said. The row follows speculation that Labour will introduce a list of approved candidates for general elections, subjecting them to the same rigorous selection procedures used in by-elections. Constituencies arrange their own shortlists for general elections but an NEC panel does so for by-elections.
The Conservatives also have plans under way to change adoption procedures and have scrapped their previous list of approved candidates. However, Lord Parkinson said any selection changes introduced by the Tories would not "ride roughshod" over local wishes.
The by-election is an early popularity test for both the Labour government and Mr Hague. Some observers were surprised that the Conservatives chose Mr Randall rather than any one of a number of high-profile former MPs anxious to resume a career in the Commons. But the local association instead chose to rely on the appeal of a local man whose values, like his department store, are described as "old-fashioned".
The Liberal Democrats' campaign in Uxbridge was launched yesterday by Nick Harvey MP, the party's chairman of campaigns.Reuse content