Harman's cunning plan: Twin shadow ministers with MP hopefuls to win Tory marginals

Don't tell the people of Bernkastel. The pretty 15th-century town on the banks of the river Mosel in Germany, twinned with Milton Keynes, has a new rival – Harriet Harman.

Labour's deputy leader has devised a strategy that, the party hopes, will help secure victory at the polls in 2015: all 100 members of Ed Miliband's frontbench, including 26 shadow cabinet ministers, have been "twinned" with the 100 top target seats around the UK to give candidates a boost.

Ms Harman, who is twinned with Labour's candidate in Milton Keynes, Andrew Pakes, says the idea is to get shadow ministers, many of whom are defending safe seats in Labour's northern heartlands, to adopt a "marginal mindset" and listen to the concerns of voters they need to win over.

Before Mr Miliband's "One-Nation Labour" landmark speech last week, Labour figures were warning that the party had to do more to appeal to those voters across the South who were crucial to Tony Blair's three election victories. His game-changing speech sent a message that he wants to appeal to the whole country, but aides said the words had to be backed up with street-by-street fighting in marginal seats.

Ms Harman told the party's conference: "We've got to be the voice speaking up for the young couple in Dartford, as well as the young couple in Darlington. We've got to speak up for the pensioner in Gloucester, as well as in Grimsby. The commuter in Milton Keynes as well as in Manchester."

In around 70 of the top 100 Labour target seats, it is second to the Tories but the Liberal Democrat vote is large enough to turn blue to red if they back Labour. The numbers mean Labour needs to woo Lib Dem voters – a strategy which has caused some division inside the Shadow Cabinet.

One extraordinary statistic, revealed to the Progress rally in Manchester by shadow Foreign Secretary Douglas Alexander, was that of five million voters who deserted the party since 1997, one third have died.

As more Prospective Parliamentary Candidates (PPCs) are selected in the 100 target seats, they will be twinned with shadow ministers. Other pairings already made include: Yvette Cooper twinned with Bedford, where Labour's candidate Patrick Hall is fighting to overturn a Tory majority of 1,353; Douglas Alexander is twinned with Cambridge (Daniel Zeichner); Ed Balls with Dover and Deal (Clair Hawkins); Rachel Reeves with Redditch (Rebecca Blake); and Stephen Twigg with Crewe and Nantwich (Adrian Heald); Liam Byrne has been twinned with Cannock Chase (Janos Toth); Ivan Lewis with Harlow (Suzy Stride); Caroline Flint with Lincoln (Lucy Rigby); and Chuka Umunna with Norwich North and South (Jessica Asato and Clive Lewis).

A source close to Ms Harman said MPs were delighted to "get stuck in" to the must-win battles and added: "We're all fighting marginals now."