Henley-on-Thames The Conservatives will pick a candidate to replace Boris Johnson in his former constituency of Henley this week as the party moves to stage a quick by-election.

The move to usher in a replacement as quickly as possible is designed to capitalise on last week's landslide victory by David Cameron's party in Crewe & Nantwich.

The Tories are also understood to be concerned that, the longer they wait, the more ground will be gained by the Liberal Democrats, second in the constituency in 2005. Ann Ducker, 65, the Tory leader of South Oxfordshire District Council, is seen as the front-runner to replace Mr Johnson.

John Walsh, the Conservative agent in Henley, said that the party had pencilled in June 26 as the most likely date for a contest.

Mrs Ducker said she was surprised that she was regarded as the front-runner and added: “None of us would be a Boris. Boris was larger than life and a terrific personality. I'm very different.”

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