Conservative Party leader David Cameron visits Swindon

He warned that anything but a "decisive" Tory victory on May 6 would leave Labour in charge as he sought to fight off a surge in public support for the Liberal Democrats.

Mr Cameron also declared that Swindon North and South would be "key battlegrounds" in deciding which party formed the next government.

He declined to follow Gordon Brown in admitting he had "lost" to Lib Dem leader Nick Clegg in the presentation stakes during the first leaders' debate on TV.

He said he was confident he had got his message across on key issues and would continue to run a "positive" campaign despite pressure to attack the third party.

Addressing an audience of mainly older voters, including his own parents, in a pub garden in Swindon, he was asked if he too believed he had lost to Mr Clegg in the debate and that the Lib Dems were now regarded as the party offering "change".

"People will judge the debates, people will decide what matters in these debates. What I think matters the most is getting your case across about the change you want to bring," he said.

"Whether it's the need to control immigration, whether it's the need for a tougher approach on crime, whether it is how we improve our health service, on all of those subjects, people watching at home can hear how the potential leaders of our country actually believe about those things," he said.

Mr Cameron went on: "If you want real change, if you want the job to be done, the only way to get it done is to have a Conservative government.

"If you want to wake up on May 7 and be absolutely certain that you've got new leadership in this country and are not stuck with another five years of Gordon Brown, stuck with dithering and despair and depression, the only way to get that is a decisive Conservative vote.

"My response to all that is happening in this campaign is to accentuate the positive.

"Never mind what the others are doing, let's concentrate on what we are going to bring to this great country.

"It is positive energy, ideas, optimism, leadership, values to get the country moving that people want and that is what they are going to get from the Conservatives each and every day for the next 18 days of our campaign."

The latest polls confirmed early findings that Nick Clegg's strong performance in the first leaders' debate had given the Lib Dems a massive boost, one even giving the party an overall lead.

All produced figures that would result in a hung parliament if repeated across the country and suggested the Tories were suffering far more than Labour - dipping by as many as seven points and in danger of remaining the second biggest party in the Commons.

The Tories - although still leading in the other polls - will be seriously concerned at the dramatic erosion of their public popularity as the campaign nears the end of its second week.

Mr Brown told the BBC the debate had "thrown the campaign wide, wide open" and that he "lost" on presentation and style.

"But I've learned at the end of the debate, substance will come through," he told The Andrew Marr Show.

Mr Cameron delivered his speech in summer-like conditions in the garden of the appropriately-named The Sun Inn as he visited Swindon - where the party would need to take two seats from Labour if they were to stand any chance of forming the next government.

He hit out at Labour "lies" that benefits such as winter fuel payments, free bus travel and TV licences and pension credit would be cut - insisting they were safe "no ifs, no buts".

OAPs would have more money as the state pension would be relinked to earnings from 2012 thanks to the "difficult choice" to bring forward to 2016 the increase in the retirement age to 66, he said.

Other measures to help older people financially, he said, would include a two-year council tax freeze and axing rules that force people to buy an annuity at 75.

Mr Cameron hit out at Gordon Brown, accusing him of presiding over the "outrage" of pensioner poverty.

One pensioner had written to him saying he was so hard up that he had been forced to sell his father's First World War medals - including a Gallipoli Star - and his collection of trench art from Ypres "to make ends meet".

"What an outrage that this should happen in our country," he said.

"Gordon Brown talks about his moral compass.

"But when his tax raid took billions from private pensions, when he recently confirmed the basic state pension is going up by less than inflation, when social care penalises those who have worked hard and saved hard by forcing them to sell their home, when he proposes a new death tax, taking up to £50,000 of what you have when you die to pay for your care, when he is fighting this election on plans that potentially scrap the Disability Living Allowance for the over-65s and to scrap the Attendance Allowance for future claimants, I've got to ask: just where is that moral compass pointing?"

The Tory leader also said he wanted older people to form "the army" of his Big Society ideas - in which the public play a bigger role in running and shaping public services - and pointed to his parents, Ian and Mary, as the inspiration, "The Big Society is our big idea, but I need to say thanks to my mum and dad because really it's down to them.

"They showed me how a Big Society could work every day I was growing up. And if we win, nothing will make me happier than to be able to take that idea - using the values they gave me - to help bring our country together.

"My father used to work really long days but he always had time for the Parochial Church Council and the Parish Council.

"My mother was a magistrate. She used to come home and tell us all the stories about the Newbury bypass protesters and Swampy up his tree.

"But the thing that strikes me looking back is how they wore their public service so lightly.

"This wasn't some great duty with a capital D that they felt the need to grandstand about.

"Like so many of their generation the values implicit in the Big Society - duty, responsibility, obligation - are instinctive; it's just what you should do.

"Older people can be the army of the Big Society to bring new life to our communities."

Mr Cameron also defended his party's plans to exempt all but estates worth more than £1 million from inheritance tax - a move opponents say will only benefit a small number of wealthy families.

"This is a tax that should only be paid by the rich. It should not be paid by people who work hard, who save hard, who pay down the mortgage, who do the right thing and want to leave their family home to their children and not the taxman," he said.

Mr Cameron, who earlier visited an aid agency warehouse in Birmingham to highlight the party's plans for international development on World Poverty Day, ended his day's campaigning to return home to help his wife Samantha celebrate her 39th birthday.

"In order to keep my marriage healthy and strong I think it's time to go and spend some time with her," he joked.