Voters are being kept "in the dark" over future spending cuts and tax rises, the influential Institute for Fiscal studies has said.
A detailed study of the party manifestos by the IFS concluded that none of the main three parties had provided "anything like full details" on plans to cut the deficit over the next five-year Parliament.
It said voters were being offered "genuinely big differences" and "a real choice" at the election but at best could "only see the broad outlines of that choice".
The Conservative party's plans do not add up, the IFS said, with only one tenth of its welfare cuts revealed. The Tories will have to make £40 billion of cuts by 2020 to keep within its plans, while its tax policies represent a net giveaway.
"Despite planning for more austerity, the Conservatives’ detailed tax policies amount to a net giveaway," Carl Emmerson, deputy director of the IFS, said.
Labour's plans are "considerably more vague" than the Tories, the think tank said, concluding that an Ed Miliband government may only need to make £1 billion of cuts.
The Liberal Democrats are being more open about its plans than the big two parties with its proposals to make £12 billion of cuts, but these are based on two optimistic claims: crackdowns on tax avoidance and benefit fraud.
The SNP has a "considerable disconnect" between its anti-austerity "rhetoric" and its plans. Government spending would freeze under its plans, but at a lower level than Labour, suggesting there would be no obstacle for a post-election deal.
The IFS added that all three of the main Westminster parties' plans to raise revenue from tax avoidance were based on "made up assumptions". The Tories have pledged to find £5 billion from tax avoidance, Labour has said it will raise £7 billion while the Liberal Democrats plan to find £7.5 billion.
"The SNP are the one major party not to have used largely made up assumptions on tax avoidance to try to make their sums add up," Mr Emmerson said.
Jonathan Isaby, Chief Executive of the TaxPayers' Alliance, called on the party leaders to be more honest about their spending plans in the run-up to polling day in two weeks' time.
"The politicians seeking our votes owe it to taxpayers to come clean about what spending the country can, and cannot, afford," he said.
"This candour has so far been noticeably absent in the election campaign, with politicians failing to acknowledge the dire state of the public finances and instead clambering over each other to make additional and apparently unfunded spending pledges.
"Politicians are talking the talk on deficit reduction but there remains precious little indication they're willing to walk the walk."
The Independent has got together with May2015.com to produce a poll of polls that produces the most up-to-date data in as close to real time as is possible.
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