The UK Independence Party is relaunching its domestic policies to show it is not just a single issue group and can take on the Tories.
Mr Knapman hopes defections to UKIP will follow
UKIP leader Roger Knapman said he wanted to fill the void left by the "rush to the centre" by other parties.
In the past, UKIP had offered "negative opposition" but would be more positive in its policy review, he said.
The party's European Parliament leader, Nigel Farage, said the new policies would be "to the right" of the Tories.
But the party still wanted support from people who had previously voted for Labour or the Liberal Democrats, he said.
UKIP's central appeal has always been its call for Britain to pull out of the European Union.
Now it is using a policy review to "deepen" its other policies, particularly on education, international trade, immigration, tax and devolution.
UKIP POLICY PLANKS
Creating English Parliament
It wants to capitalise on complaints from some Conservative right-wingers that new leader David Cameron is moving too far into the centre.
At a news conference in Westminster, Mr Knapman said UKIP was targeting the 5m voters who had abandoned the Conservatives since 1992.
"The traditional parties have left voters with a Hobson's choice between New Labour and Blue Labour: authoritarian, centralised visions of a Britain which few would choose to live in," he said.
Mr Knapman promised to offer a "more positive vision".
"It is true in the past few years UKIP has offered negative opposition: say no to the Westminster and Brussels consensus, no to the EU, no to ID cards, no to the war in Iraq."
Despite its claims about unrest among Tory supporters, UKIP is so far unable to unveil new defectors or cash donors.
But Mr Knapman claimed it could double or treble its membership, currently 20,000, over the next two years. There had been a big increase recently in people asking for information about the party.
Mr Farage admitted UKIP had endured a difficult period, with the acriminous departure of former TV chatshow host and MEP Robert Kilroy-Silk.
But now it had a great opportunity, he argued.
"We are without any shadow of a doubt parking our tanks on David Cameron's abandoned lawn," he warned.
UKIP last year promised a campaign for a national referendum on British membership of the European Union.
Mr Farage said it was not the right time for that campaign as British membership of the euro and the European Union constitution appeared to have gone away as issues.
On education, UKIP wants to allow schools to select pupils.
The party also wants much stricter limits on immigration - allowing only as many people to into Britain as leave the country.
The party also wants England to have its own parliament - in the way Scotland and Wales have devolved bodies.
Scottish MPs and Welsh MPs would sit in the devolved bodies as well as at Westminster - rather than having two sets of elected politicians.
And any devolved decisions would have to be vetted by the UK Parliament to ensure they did not damage other parts of the UK.
UKIP is also looking at the idea of a "flat tax" where people pay the same rate of tax whatever their earnings.
And it wants the UK to negotiate its own trade deals rather than acting through the EU.
In the 2004 European elections, UKIP took 16.1% of the vote. However, in last year's general election it got 2.2% of the UK vote, and failed to take any seats.
It plans to field about 500 candidates in this year's local elections. The Conservatives are likely to have more than 2,000 candidates.