After Ed Miliband's audacious pledge  to reintroduce the 10p tax rate, funded by a mansion tax on houses worth more than £2m, George Osborne is under even greater pressure from Conservative MPs to play a "trump card " when he delivers the Budget on 20 March. There's frustration among the Tories that the 10p tax rate, a measure championed by  a Conservative MP, Robert Halfon, was taken up by Labour before Halfon's own party. If he wants to avoid a backlash, the Chancellor now has no choice but to announce significant tax cuts when he steps up to the despatch box next month.
In an article  for today's Daily Telegraph, Graham Brady (profiled  by Caroline earlier this year), the chairman of the powerful 1922 Committee of backbench Tory MPs, wastes no time in setting out hs Budget wishlist. While praising the Chancellor's cuts to corporation tax (which has been reduced from 28 per cent to 23 per cent and will fall again to 21 per cent next year), he urges him to "go further".
Brady's principal demand is for Osborne to abolish Air Passenger Duty - "the highest aviation tax in the world" - which the Chancellor increased  by eight per cent in last year's Budget. He points to a study by PricewaterhouseCoopers which found that scrapping the tax would deliver an immediate economic boost of 0.5 per cent of GDP. This, Brady pointedly notes, is "not to be sneezed at in these days of anaemic growth."
But when I spoke to Robert Halfon earlier this week (undoubtedly now the most influential backbench MP), he told me that cutting Air Passenger Duty would be the wrong move. "In times like this, flying is a luxury, it's not something you have to do" he said. "It's [reducing Air Passenger Duty] not the best way to help low-earners".
Having criticised Labour's 10p tax proposal on the grounds that it would only mean an extra £34 a year for a family (once benefit withdrawal is taken into account), Halfon is still pushing for Osborne to adopt his policy in full: a reintroduced 10p rate on earnings between £9,440 and £12,000 (Miliband's proposal would only apply to the first £1,000 of earnings over the personal allowance).
But with Osborne having unambiguously ruled out the introduction of a "mansion tax" ("this party of home ownership will have no truck with it," he said in his Conservative conference speech), the question remains how the Chancellor would pay for a 10p rate. Halfon has proposed funding the measure by ring-fencing the extra revenue from the 45p rate (on the assumption that a lower top rate of tax will benefit growth). But with growth likely to remain anaemic or non-existent, Osborne will have little room for manoeuvre, not least because he has already promised to raise the personal allowance to £10,000 by the end of this parliament. Whether or not Tory MPs secure the tax cuts they wish to see may yet depend on whether the Chancellor, a fiscal conservative to his core, is finally willing to tolerate a higher deficit.