The Conservatives have launched their manifesto for businesses with pledges to cut red tape and help entrepreneurs.
Mr Howard and Mr Letwin fronted Monday's press conference
The document - Action for Business - includes a 10-point policy plan which includes lower business taxes and more government support for UK exporters.
Both Labour and the Liberal Democrats have also stressed their commitment to helping UK businesses thrive.
Ahead of the launch Tory leader Michael Howard said voters should use their votes on 5 May to "take a stand".
Tony Blair was "praying" the UK would "sleepwalk its way to another five years of Labour".
Mr Howard said voting Labour would be a vote for "four more years of higher taxes".
Tory business plan
Rejuvenate DTI to become "champion" of British business
Replace Labour's 'better regulation' with "genuine" deregulation
Create business-driven skills agenda
Lower taxes and simplify tax system
Robust action to reduce business crime
Support British ideas to make British profit
Action to promote freer, fairer trade
Strengthen support for exporters
Action on transport to aid business
Review national strategy for energy
He said: "If I came up to you in the street, took money out of your pocket and threw it down the drain, that would be a crime.
"Well, that's what Mr Blair's government does every day of the week. But you don't have to settle for this.
"It's time to take a stand against government waste. People work hard for their money. They deserve a government that takes a stand, stops the waste and gives them lower taxes and value for money."
Shadow chancellor Oliver Letwin meanwhile said under Gordon Brown's stewardship the government had "run out of money" and the country now had a "substantial overdraft".
Mr Blair described the Tory business manifesto as "flimsy" and said Labour was the party of "economic confidence".
Trade Secretary Patricia Hewitt said: "The Conservatives claim to be the party of business, but today they run away from the economy and they have given up on business."
She added the Tories' business manifesto "is utterly threadbare - they are campaigning, not on a serious programme for government but on a serious of issues around which they hope to generate fear and grievances."
But Mr Brown also pledged to cut the regulations firms faced, starting by reducing the number of inspections by 1 million a year and the number of inspection agencies from 35 to nine.
"I understand that regulation and red tape and bureaucracy are challenges in every industry in the world," he said.
And he went on to admit he should have taken these steps "before now".
The Lib Dems said their party would set business free and highlighted their plans to scrap the DTI.
Treasury spokesman Lord Newby will tell business leaders: "Liberal Democrats recognise that business needs the freedom to generate economic growth - yet they are held back, struggling under a mountain of government rules, tax complications, bureaucracy and inspection."
In a speech to the British Chamber of Commerce Mr Howard said that the UK had fallen from fourth to 11th in the world competitiveness league and income per head was lower than Ireland's.
"When you hear Gordon Brown going on about the need to make the European economy more like America's, you might think he agreed with me," he said.
"The great irony is that he's actually making Britain's economy more and more like those of continental Europe. Europe should be a market for British business, not an economic model."
Mr Brown said: "While Labour will lock in stability that is the top priority of business, the reckless and irresponsible Conservative proposals - that [Tory ex-premier] Mrs Thatcher would never have countenanced and that as shadow chancellor I could never endorse - would put stability at risk."