One of the most closely-contested general elections for decades formally gets under way today, with David Cameron due to launch the Conservative campaign in Wiltshire.

Mr Cameron addressed the party faithful and media representatives in Corsham, accusing Labour of planning a £3,000 tax hike for every working family, warning of a "stark choice" facing the country after a symbolic final audience of his term in office with the Queen.

Labour insisted the Tories' tax claim was "totally made up" as it prepared to launch an offensive over Mr Cameron's promised in/out referendum on Britain's membership of the EU.

Launching the Opposition's business manifesto, leader Ed Miliband said a Tory victory poses a "clear and present danger" to jobs and prosperity and made it a Labour commitment to "return Britain to a leadership role" in Brussels.

Prerogative to order the dissolution of Parliament no longer rests with the monarch, under new rules fixing each term at five years, but Mr Cameron nevertheless made the short journey to Buckingham Palace to recommend she issue a proclamation summoning the new parliament on May 18.

Deputy Prime Minister Nick Clegg followed Mr Cameron into the Palace for a separate private audience - as Lord President of the Privy Council he has an obligation to do so - before focusing on the NHS at a Midlands seat the Liberal Democrats are fighting to hold.

Parties have been sparring in earnest for months but every day from now until the eve of polling on May 7, leaders will be on a final push around the UK in the search for those crucial votes that could swing the result in their favour.

With the majority of polls still showing the two established Westminster parties running neck-and-neck, increasingly bitter blows are being traded over the implications for public spending and tax in each of their deficit reduction plans.

Mr Cameron - speaking before heading to Corsham for a campaign rally - will fuel the argument by unveiling Conservative calculations about potential tax rises if Labour returns to power.

It said that if the Opposition sought to balance the books with an equal mix of spending cuts and tax rises - an approach it claims Mr Miliband prefers on the basis of a 2010 magazine interview - it would mean every working household's bill rising by £3,028 a year.

Mr Balls has ruled out raising national insurance, the main rate of VAT or the basic or higher rates of income tax, and Tories claim his promised restoration of the top 50p rate on £150,000-plus salaries would raise little.

"In 38 days' time you face a stark choice: the next prime minister walking through that door will be me or Ed Milliband," Mr Cameron will say.

Wiltshire Times:

  • David Cameron speaks in Corsham today.  Picture: Stefan Rousseau/PA Wire

"You can choose an economy that grows, that creates jobs, that generates the money to ensure a properly funded and improving NHS ... and a government that will cut taxes for thirty million hard-working people.

"Or you can choose the economic chaos of Ed Miliband's Britain - over £3,000 in higher taxes for every working family to pay for more welfare and out-of-control spending. Debt will rise and jobs will be lost as a result.

"Ed Miliband pays lip service to working people while planning to hike taxes and increase debt. After five years of effort and sacrifice, Britain is on the right track. This election is about moving forward - and as Prime Minister here at Number 10, that's what I will deliver."

Former Commons speaker Baroness Boothroyd said she was "dismayed" by the Prime Minister's decision to launch the Tory election campaign at a media event outside 10 Downing Street.

She said this gave the Conservatives an unfair advantage and that Ed Miliband should be allowed a right of reply in the same place.

Lady Boothroyd said "rules of fair play should apply", adding: "The Prime Minister made an election address in his capacity as a party leader. I believe Mr Cameron's departure from previous practice confers an unfair advantage on a governing party."

Shadow chief secretary to the Treasury Chris Leslie said: "These are totally made up figures from a desperate David Cameron who has raised taxes on working people.

"Under the Tories families have lost over £1,100 a year on average from tax and benefit changes, while millionaires have been given a huge tax cut.

"Labour will reverse the Tory tax cut for millionaires and cut taxes for millions on middle and low incomes through a lower 10p starting rate of income tax."

Labour yesterday urged the Tories to set out to voters where exactly the axe would fall in £12 billion of benefit cuts central to Chancellor George Osborne's plan to restore the economy to an annual surplus by 2018/19.

The independent Institute for Fiscal Studies (IFS) warned that the planned cuts will be "really tough" to achieve, involving "pretty dramatic" reductions in areas such as housing and disability benefits over the next three years.

Work and Pensions Secretary Iain Duncan Smith said a quarter had already been publicly identified but the party may not think it "relevant" to explain where the rest of the cuts will fall before the election.

It came as Conservatives accused Labour of "letting the cat out of the bag" on plans to increase state borrowing, after election campaign vice-chairwoman Lucy Powell said the party "may use some investment borrowing".

Unlike the Tories, who have committed to balancing the overall budget by 2017/18, Labour has promised only to eliminate the current deficit on day-to-day spending by the end of the next Parliament, leaving open the option of borrowing money to invest in capital projects.

First poll brings mixed news

There was mixed news for the main parties in the first poll to be released since the campaign formally began.

Tory peer Lord Ashcroft's latest weekly survey showed the Conservatives were up three points on last week, to 36%, two points ahead of Labour, which gained one point. Last week they had been neck-and-neck.

However, the poll suggests Labour leader Ed Miliband is narrowing the gap on David Cameron in personal terms.

The Lib Dems dropped two points and are now at 6%, while Ukip fell two points to 10% - marking the lowest rating for the latter party since May 2014.

The Greens went ahead of the Lib Dems, rising two points to 7%, while there was bad news for the SNP as it fell two points to 4%.

Nick Clegg has insisted his "plucky party" can defy the polls, claiming that in the "50 or 60" seats where the Lib Dems had an MP or an effective presence on the ground, they were doing far better than opinion polls suggested.

On a visit to Solihull, a knife-edge marginal with a Lib Dem majority of just 175, he said the campaign would allow people to hear his party's side of the story.

On a visit to the Brueton Park nature reserve in the constituency, the first stop of the campaign tour, Mr Clegg said: "What you have got to ask is how are we doing in those 50, 60 seats where we have MPs, we have campaigners, we have councillors.

"There, the picture is completely different to the national snapshot polls because there people hear the Liberal Democrat side of the story - which is one we are very proud of - which is about a plucky party stepping up to the plate back in May 2010 when the country desperately needed it."

Wiltshire Times:

  • Ewan Rowe, 16, poses for a selfie with Liberal Democrat leader Nick Clegg during his visit to Parkridge Centre, part of the Warwickshire Wildlife Trust in Solihull. Picture: Steve Parsons/PA Wire