Labour will fight the general election on a cast-iron promise not to raise VAT in an attempt to put the Conservatives – who have stopped short of such a pledge – under pressure on the issue.

Ed Balls, the shadow Chancellor, will announce tomorrow that the Labour manifesto will include a “clear pledge” not to increase VAT in the 2015-20 parliament. Speaking in Birmingham, he will say: “We will not put up VAT. And we will not extend it to food, children’s clothes, books, newspapers and public transport fares.”

George Osborne, the Chancellor, has insisted the Tories have no plans for any tax rises after the election. But Labour points out that the Tories made the same statement about VAT before the 2010 election, only for Mr Osborne to increase it from 17.5 to 20 per cent in 2011 to raise £13bn a year towards deficit-reduction.

The Tories accuse Labour of basing its May election campaign on two untrue “scare stories” – that a Cameron government would hike VAT and cut the NHS.

Income tax league: the UK towns that pay the most and least tax Show all 10 1 /10 Income tax league: the UK towns that pay the most and least tax Income tax league: the UK towns that pay the most and least tax Elmbridge Income tax league: Elmbridge in Surrey is nicknamed the ‘Beverly Hills’ of Britain. Its residents include tennis champion Andy Murray AFP/Getty Images Income tax league: the UK towns that pay the most and least tax Chilterns Income tax league: The Chilterns is in third place, with tax take per person standing at £12,700 Income tax league: the UK towns that pay the most and least tax Windsor and Maidenhead Income tax league: Windsor and Maidenhead is number seven on the list of areas with the highest rates of income tax Andrew Smith/Geograph Income tax league: the UK towns that pay the most and least tax South Buckinghamshire Income tax league: South Buckinghamshire residents paying £13,600 on average Green Baron/Wiki Commons Income tax league: the UK towns that pay the most and least tax London Income tax league: Despite being home to almost 10 per cent of the world's billionaires, London is only number 14 on the list Getty Income tax league: the UK towns that pay the most and least tax Sevenoaks Income tax league: Knole House in Sevenoaks, where local residents pay some of the highest rates of income tax in the UK Income tax league: Knole House in Sevenoaks, where local residents pay some of the highest rates of income tax in the UK Income tax league: the UK towns that pay the most and least tax Stoke-on-Trent Income tax league: Stoke-on-Trent was the fifth lowest on the list, with residents paying an average of £2,580 in 2011/12 Income tax league: Stoke-on-Trent was the fifth lowest on the list, with residents paying an average of £2,580 in 2011/12 Income tax league: the UK towns that pay the most and least tax Kingston upon Hull Income tax league: Kingston upon Hull is one of the areas where residents pay the least income tax Nigel French/PA Income tax league: the UK towns that pay the most and least tax Blaenau Gwent Income tax league: Blaenau Gwent, in South Wales, is second from the bottom out of 401 areas at a £2,460 average ALAMY Income tax league: the UK towns that pay the most and least tax Blackpool Income tax league: Blackpool residents pay the least income tax out of all the 401 regions, at £2,290 a year Getty Images

Mr Balls will say tomorrow: “We will not raise VAT because it’s the tax that hits everyone. It’s the tax that hits you every day. And it hits pensioners and the poorest hardest. That Tory VAT rise hit the living standards of millions of people. It led to higher prices for everyone – helping inflation hit 5.2 per cent when it was raised.”

The shadow Chancellor will add: “VAT is the tax that every Tory government in the last 40 years has raised. But no Labour government has ever hiked up the main rate of VAT.”

Yesterday, Ed Miliband tried to tackle the biggest threat to Labour’s election prospects – the surge by the Scottish National Party. Speaking in Clydebank, Scotland, he claimed there was an “unholy alliance” between the Tories and the SNP. Labour claims the Tories are raising the spectre of a Labour-SNP deal in a hung parliament to damage Labour in both Scotland and England. Labour’s private polls suggest that one in 10 of the Scots intending to back the SNP realises that doing so could put the Conservatives in power. The finding has raised Labour’s hopes of winning back some of the party’s former supporters who have stuck with the SNP since last September’s referendum on independence. Labour plans to to “turn” about half of these voters, which would greatly reduce Labour’s losses to the SNP.

Miliband claims there is ‘an unholy alliance’ between the SNP and the Conservatives (Getty)

Opinion polls suggest that Ed Miliband’s party could even change places with the SNP, which currently hold six of Scotland’s 59 parliamentary seats to Labour’s 41.

There is a fierce debate inside Labour about whether to go head-to-head with the SNP in being an “anti-austerity party.” Some Labour MPs want Mr Miliband to trumpet that their party could spend an estimated £30bn more than the Tories. But other Labour MPs are warning that such a boast would cost votes in England. One Labour source said: “It might help us in Scotland, but it would kill us in England.”

Mr Miliband said yesterday: “Every vote in this election that might allow the Tories to be the largest party is a vote for Tory austerity to continue.”