Gordon Brown will have “bottled” the most important political decision of his career if he fails to call a general election next week, George Osborne told The Times yesterday.

The Shadow Chancellor stepped up the pressure on Mr Brown, accusing him of lying when he claimed to be “entirely focused” on running the country.

“If the election is off then he’s got a lot of explaining to do as to why he’s spent the last couple of months engaged in political posturing rather than getting on and running the country,” Mr Osborne said.

His comments came as the Shadow Chancellor revealed that the Conservatives have prepared two further significant tax-cutting packages on top of his inheritance tax announcement on Monday. He said that both would be announced in the course of an autumn election campaign.

He made clear that his proposal to raise the threshold of inheritance tax to £1 million that has electrified the Conservative conference in Blackpool was just the opening salvo of a barrage of Tory tax cuts.

A package of cuts in personal taxation has been prepared and would be unveiled early in a campaign this autumn. A second set of measures to simplify businesses taxes – including a cut to the rate of corporation tax – has also been signed off by the Shadow Chancellor.

Mr Osborne accused the Prime Minister of lying when he claims to be entirely focused on running the country and says he will have “bottled” it if he doesn’t call an election.

He began a counter-attack against Labour’s critique of his plans to raise £3.5 billion in taxes on wealthy foreigners living in Britain.

It is the prospect of two more significant packages of tax cuts that will do most to cheer activists as they prepare to hear David Cameron today, however. “What I did yesterday was a reform of capital taxation but we also have proposals for business and corporate taxation,” he said, adding that he was also looking at “the whole area of personal taxation”.

Having endured the political pain of pledging to introduce green taxes, Mr Osborne made clear that he was looking forward to revealing what a Conservative government would do with the proceeds.

He refused to be drawn on specific pledges but said that he had a “good idea” of how much he had to spend on personal tax cuts if Mr Brown calls an election next week. “We will use the money we raise from any environmental taxes to reduce taxes pound for pound elsewhere. We have established the idea of a ‘family fund’ which would make sure that this money is ring-fenced so every penny will be used for tax reduction.”

Privately, senior Tories say across-the-board cuts to income tax are unlikely but hint that married taxpayers can expect to benefit.

Mr Osborne said business needed cuts if Britain was to remain competitive not just with the emerging giants of China and India but low-tax regimes, such as the Irish Republic.

“I have worked with PriceWaterhouse Cooper on what we can do to simplify the corporate tax system, including reducing the corporation tax rate.”

Both packages are ready to be unveiled immediately. “If there is a general election this autumn then we would set out those proposals in an election campaign. If not then we will wait until closer to the date of the election whenever it may be.”

He declines to predict whether the Prime Minister will go to the country this autumn. “I cannot get inside Gordon’s mind. I spent two years shadowing him and it remains a mystery as to what motivates the man.

“He’s left us in this position where either we have had more advanced notice of when a general election is going to be than almost any opposition have had in recent times or he bottles it.

“If the election is off then he’s got a lot of explaining to do as to why he’s spent the last couple of months engaged in political posturing rather than getting on and running the country.

“When he says, ‘My mind is entirely focused on governing the country’, I’m afraid that is a statement that bears no relation to the truth.”

The Shadow Chancellor has been criticised for failing to prepare the Conservatives for the “Brown Bounce”. “I don’t underestimate him but I don’t overestimate him either,” he said.

Mr Brown’s speech “opened a door” for the Tories because he failed to set out a vision for Britain’s future. The “spotlight” of an election campaign will expose Mr Brown’s shortcomings, “I am confident that the lack of substance and the record will be exposed.”

In an atmosphere of naked electioneering, he took on Labour’s initial attempts to unpick his tax proposals branding as “ludicrous” its claim that there is a £2.85 billion shortfall in his figures. “On the costings of the policy and the number of nondomiciles I think we are on extremely robust territory. The claim by the Labour Party that there are only 15,000 nondomiciles in Britain who have got offshore incomes of more than £62,000 is patently ludicrous.”

The Tories are furious that Labour claims its rebuttal is based on official figures because Ed Balls, then Economic Secretary, told the Commons the data was not collected.

“I have written to the Permanent Secretary [of the Treasury, Nicholas Macpherson] asking for an explanation,” he said.

Mr Osborne says that the tax cuts for those with estates up to a £1 million is balanced by proposals to give low-paid couples an extra £3 billion in tax credits. He admits, however, that it is likely to take “the length of a Parliament” – five years – for the tax credit rises, paid for in anticipated savings in welfare, to be paid in full.

He denies the claim, however, that handing immediate tax cuts to the rich while making the poorer wait for up to five years will increase inequality.

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