Mr Brown backed a Labour document analysing Liberal Democrat spending pledges which looked like a carbon copy of Conservative attacks on Labour before the last General Election. "Their spending plans would mean large tax increases for the British people," he said.
The Liberal Democrat candidate, Chris Davies, welcomed Mr Brown's arrival: "I'm delighted to be attacked for wanting to spend money on education." His response highlighted the fact that Labour is attacking the Liberal Democrats for putting a cost on many policies which are similar to Labour's own.
The Labour dossier puts a pounds 340m price tag on a Liberal Democrat pledge of two years' pre-school education for every child - which is also (uncosted) Labour policy.
The dossier includes the cost of an extra 500,000 students in higher education, the restoration of free NHS eye and dental checks and the extension of home insulation grants and energy efficiency schemes, all of which Labour supports.
It concludes that Liberal Democrat plans would put the equivalent of 5p in the pounds on the standard rate of income tax. Labour accuses the Liberal Democrats of wanting to impose a pounds 650-a-year 'tax hike' on the typical local family, on top of the pounds 800 a year already imposed by the Conservative government.
The by-election takes place next Thursday.
has developed into a fierce battle between the two Opposition parties to seize the seat vacated by the death of Conservative Geoffrey Dickens, with all observers assuming that no seat can be held by the Government in any by-election.
The second phase of Labour's two-pronged assault on the Liberal Democrats follows an attack on Mr Davis over the issue of drugs which has suprised many Labour members by its ferocity. The Liberal Democrat has been attacked by the 'church-going' Labour candidate Phil Woolas for backing an inquiry into the de-criminalisation of cannabis. Mr Woolas, whose slogan is The Strong Choice is described as a 'practising Anglican who believes in strong family values and responsible, disciplined upbringing for the young.'
The ruthlessness of Labour's campaign, managed by Tony Blair's close ally Peter Mendelson, the MP for Hartlepoool, has seen battle hardened Shadow Cabinet members shift awkwardly in their seats when defending it in private.
Mr Wooas was unapologetic yesterday: "The issue is not just drugs and taxes, it is the fact that the Liberals are not a serious party," he said
The Lib Dems yesterday stuck to "their issue" - education, and published a survey of headteachers in the constituency in which four out of five said their classes were larger than the ideal size..
The Conservative campaign has been buoyed by a misreading of last week's Guardian/ITN opinion poll error, in which ITN corrected a 29 point Labour lead to a 15 point one. Analysis of the unadjusted figures, which probably provide a better guide to trends, showed the Conservatives up only six points, more at the expense of the Liberal Democrats (down four) than Labour (down 2).