Speaking to Western Morning News as Labour held its South West conference at the weekend in Exeter, the MP claimed its opposition to scrapping minimum wages for farm workers and fruit pickers showed how it would be a better guardian of rural communities than either the Liberal Democrats or the Tory party.
Labour holds only five of 185 county council seats up for grabs across Devon and Cornwall at elections in May. But she said Labour candidates would not be there to make up the numbers: "We want to make progress in the South West. They won't be paper candidates."
While historically the region's third biggest party – outside urban Plymouth and Exeter – the London MP indicated the party wants to overtake the Liberal Democrats.
She said: "The reality is the Liberal Democrats have thrown in their lot in with the Tories in government. The cuts in services that are causing so much concern and stagnation in the economy is causing problems particularly for young people. The Liberal Democrats are not the opposition."
Asked why rural Westcountry voters should put their faith in Labour, she claimed Labour-controlled Exeter City Council had built more affordable houses than all the other authorities in the region put together, tackling one of the peninsula's biggest issues.
And she has challenged Conservative and Liberal Democrat MPs in the region to join Labour in opposing the abolition of the Agricultural Wages Board (AWB) at a decisive Commons vote.
Ministers want rid of the 60-year-old body, which survived Margaret Thatcher's cull of the quangos in the 1980s, claiming modern employment laws and the minimum wage has rendered the body a "burdensome anomaly". It sets pay for farm workers of between £3.11 and £9.40.
Ms Harman said: "The abolition of the Agricultural Wages Board would affect 23,460 agricultural workers in the South West, pushing down wages and striking another blow to living standards for working people. This is a major issue in the South West where nearly a fifth of all jobs hit by the abolition of the Agricultural Wages Board are located."
She added one-time Lib Dem rural affairs spokesman Andrew George, MP for St Ives, is against its abolition but "Lib Dem MPs have voted with the Tories to abolish it".
Labour made huge strides in the 1997 general election off the back of the Tony Blair-inspired renaissance – winning Exeter, two seats in Plymouth and even one in Cornwall. But that has been reduced to MPs Ben Bradshaw in Exeter and Alison Seabeck in Plymouth Moorview.
The party's list of around 100 target seats for the 2015 general election includes the second seat in Plymouth – Sutton and Devonport, held by Conservative Oliver Colvile – but none in Cornwall, despite some believing Camborne and Redruth is a prospect.
Liberal Democrat leader Nick Clegg said the snub to Cornwall represented Labour "turning its back" on the far South West. Ms Harman said, though: "We will review the list after the local elections."
Labour now holds Plymouth and Exeter city councils following last year's local elections and has taken seats in districts in Devon and Cornwall where it is traditionally locked-out, including Dartmouth and Bideford.
