Bromley voters highlight the divide in Tory ranks

The Conservatives admitted yesterday that they still need to find "positive" reasons why people should vote for them, after they narrowly avoided a potentially catastrophic by-election defeat in one of their safest Commons seats.

Voters in Bromley and Chislehurst deserted the Tories on a scale that very nearly produced the worst swing against them since Labour came to power in 1997. The Liberal Democrats came within 633 votes of capturing the south London seat, where they had trailed in third place in last year's general election, won by the late Tory Eric Forth with a majority of 13,342.

The result is likely to provoke recriminations behind the scenes, with Tory traditionalists blaming the party leader, David Cameron, for putting off natural Tory voters in his quest to modernise the party. Cameron supporters said it proved the pace of modernisation had to be stepped up.

Francis Maude, the party chairman, admitted that the result was "a bit of a wake-up call for us - that we've got a long way further to go".

He told BBC Radio 4's Today: "David's been rightly driving a process of change. The simple truth from this election result is that we have to drive that change faster, wider and deeper, because we have to supply more and more positive reasons why people should vote for us. And I'm sure we will do."

The winning Tory candidate, Bob Neill, angrily accused the Liberal Democrats of running a personal campaign against them. "If you sometimes wonder why it is that people in this country are turned off by politics, get a mirror and look at yourselves," he told them.

The attack was rejected by the Liberal Democrat leader, Sir Menzies Campbell, who praised his party's performance as "stupendous result" which "shows that there is no confidence in Cameron's Tories in the Conservative heartlands."

Mr Neill had come under attack both from the Liberal Democrats and the UK Independence Party for his multiple roles as a member of the London Assembly, a paid member of a health authority, and a practising lawyer. The Lib Dems called him "three jobs Bob."

The UKIP candidate, Nigel Farage, claimed the campaign had shown "the arrogance of the Tory party and its willingness to take Bromley and Chislehurst's voters for granted". He added: "Mr Neill has far too many jobs and sits on too many committees."

The swing against the Conservatives was 11.1 percentage points - fractionally better than the 11.2 per cent swing against them in the Hartlepool by-election, caused by Peter Mandelson's appointment as an European commissioner, in 2004. The only other by-election in eight years to produce such a swing of this magnitude was the unusual poll in Winchester, called after the defeated Tory candidate challenged the result of the 1997 general election.

John Curtice, professor of politics at Strathclyde University, said: "With the exception of the modest progress made in May's local elections the Tory party still has to demonstrate any evidence of a revival in the ballot box.

"This suggests there is still a battle going on for who can secure the spoils of Labour unpopularity and that the current Tory lead is probably more of a testament to the unpopularity of Labour than the popularity of the Conservatives."

In public, Labour officials were avoiding any sign of gloating over a result in which their candidate tumbled from second to fourth place, behind UKIP. But in private, they drew a comforting comparison with the sort of results that they pulled off when Tony Blair was opposition leader. In the first by-election after Mr Blair's election as party leader, Dudley West in December 1994, Labour ousted the Tories with a swing of 29 per cent. Thursday's showing by the Tories compared with the sort of by-election results Labour suffered before its defeat in the 1987 general election.