Laying out responsibility, nationhood and personal freedom as the key principles, Mr Hague promised to cut fuel tax by six pence a litre as part of £8bn worth of tax breaks also targeted at pensioners, savers and families.
" There is no excuse for giving up on Britain "
But, in a pre-emptive strike at his first news conference of the campaign, Tony Blair accused the Tories of making irresponsible promises and said their economic polices lacked the credibility necessary for government.
Liberal Democrat leader Charles Kennedy was also scathing, saying the Tory manifesto was one designed by a party that already knew it had lost the general election.
Hague's 'greatest fear'
Speaking at the Tory launch in London, Mr Hague declared: "My greatest fear for the country that I love is that we will wake up one day and find that something very precious has been lost without our ever quite realising how or why we let it happen.
"Today, our spirit of enterprise is being extinguished by higher and higher taxes, regulations and conformity.
"The standards in our public services are falling and are lower than we would accept in any other area of our lives," he said.
"We are surrendering to the European Union our ability to run our own affairs.
"And the greatest danger of all is that people begin to think that all of this is inevitable."
Speaking from a modernist podium in front of a high-tech backdrop complete with the manifesto slogan "Time for Common Sense", and with senior members of the shadow cabinet sitting nearby, Mr Hague insisted voters had a choice.
He went on: "I believe in Britain. I am ambitious for Britain. And I present today the most ambitious Conservative manifesto for a generation."
" This is divisive politics and it is bad for Britain "
And Mr Hague also made a point of saying: "Britain is made up of many ethnic communities and Conservatives believe we are stronger for it."
Of the pledges in the 48-page manifesto, only two major policies have not being announced or leaked before.
One is the 6p a litre cut in fuel tax - though 3p of that had already been pledged - and forcing local councils to hold a referendum when they want to raise council tax above the rate of inflation.
In front of an audience including his wife, Ffion, Mr Hague ended the launch with the rallying call: "I trust the British people. I trust their common sense. It's time for common sense."
Mr Blair had sought to set the theme of the day by declaring that the economy would be the defining issue of the election.
After the manifesto launch, he told the BBC that the Tory plans would mean cuts to public services.
"The point is that the Conservatives are promising things without any notion of how they properly pay for them.
"The idea that you are going to pay for these promises by taking money off single parents or slashing the university budget or sacking a few civil servants...
"They will be paid for by deep cuts in basic services - schools, hospitals, the police - or by a return to debt and therefore higher mortgages and higher unemployment."
Charles Kennedy said of the Tory programme: "It is not a serious manifesto."
Speaking during a visit to Plymouth as part of his flying tour of the UK, the Lib Dem leader said the fuel tax cut proposal was "a wrong-headed policy that does not add up".
It could only be purchased "on the back of billions of pounds of cuts in schools, hospitals and support for pensioners".
The Liberal Democrats are promoting a fuel price freeze alongside more investment in ecologically-friendly forms of transport.
Green Party spokesman Mike Woodin said: "William Hague seems to be modelling himself on George Bush in America, one of the chief climate wreckers in the world."