Liberal Democrat leader Nick Clegg today firmly rejected an appeal from his Tory counterpart David Cameron for their two parties to work together.
Spurning calls from Mr Cameron for the Lib Dems to join forces with the Conservatives in a new "national movement", Mr Clegg insisted the two parties were "totally different".
The Lib Dem leader refused to discuss whether he would enter coalition talks with either Labour or the Tories in the event of a hung Parliament after the next general election.
But he made plain that he saw little similarity of approach between the Lib Dems and the Tories.
"We are totally different to the Conservatives," he told BBC One's Andrew Marr Show.
"We stand for the progressive hopes that have been betrayed in the last 10 years and I believe we can replace Labour over time."
Mr Clegg has stepped up his criticism of the Tories this weekend at the start of the Lib Dems' annual conference in Bournemouth, describing Mr Cameron as "the con man of British politics".
But the Conservatives have sought to stress their similarities with the Lib Dems, who could become kingmakers if none of the parties hold an outright majority after the next election.
In an article for The Observer today, Mr Cameron suggested the Lib Dems were creating dividing lines that did not exist between the two parties.
In areas like civil liberties, education and climate change, Mr Cameron said, there was "barely a cigarette paper" between the two parties.
"If you want rid of Gordon Brown and the big brother state, and if you care about our schools, our quality of life and our liberties, then join us in one national movement that can bring real change," he added.
But Mr Clegg immediately sought to quash any suggestion that his party would assist the Conservatives, stressing "fundamental" differences between them on taxes, Europe and political reform.
"It's all very well the rhetoric, but if you're going to ask people to vote for change then that change has got to be real change, not the kind of fake, synthetic change of Mr Cameron," he said.
He was especially critical of the Tories' civil liberties credentials, saying: "There is a profound hypocrisy to say 'we're all liberal now' on civil liberties, when they want to actually destroy one of the cornerstones that protects British liberties in the Human Rights Act."
Mr Clegg also signalled plans to target the wealthy with even higher taxes than already pencilled in.
Asked whether the rich would have to pay more compared even to plans laid out so far, he said: "Yes, unambiguously yes.
"What we believe is now necessary is a big tax switch where you close the huge loopholes that very wealthy individuals and large corporations can presently exploit, in effect escaping the reach of the taxman."
That would include bringing capital gains tax into line with income tax rates and ending tax relief on pension contributions for higher earners.
The Lib Dems also plan to raise the starting threshold for paying income tax to £10,000 to assist lower earners.
But he said that efforts to reduce Britain's debt mountain would begin with cuts in public spending rather than tax rises.
"The first port of call of filling this great gap in our public finances has to be through reductions, cuts, savings in public spending, not immediately reaching for the taxman and saying taxes should go up on ordinary incomes," he said.
He promised to protect the education budget "for the youngest children" but has warned of "savage" cuts elsewhere in spending.
He has even put activists on notice that the Lib Dems' flagship £2.5 billion pledge to abolish tuition fees might not now be affordable.
"How you want the world to be and how it is, is different and one of the things I am very keen to do in this very difficult debate about public spending is treat people like grown-ups," he said today.
Other money-saving measures suggested by Mr Clegg included ending tax credits for high earners and freezing pensions for highly-paid public sector employees.
He outlined plans today to axe at least 90 quangos, reduce the number of Government departments from 24 to 14 and cut the number of MPs from 646 to 500.
Such moves would save £1.82 billion, he said.
Among those quangos to be abolished would be all regional development agencies and strategic health authorities.
Health spokesman Norman Lamb told today's conference that too much money had been "squandered" in health and insisted that the NHS must "work better with the resources it has".
He proposed changes to the way that hospitals are paid for operations in a move that he said would save £2 billion a year.
Mr Clegg admitted today that he had paid for private healthcare for one of his sons, rather than using the NHS.
"I understand the sensitivity but I am a dad before I am a politician," he told The Sunday Times.
Bob Crow, leader of the Rail, Maritime and Transport union, accused Mr Clegg of indulging in a "race to the bottom" on public spending cuts with Labour and the Tories which would leave millions of public sector workers disenfranchised at the general election.
He said: "With the bin strikes in Leeds and Liverpool, continuing action by our members in the transport sector, the postal workers' dispute and the attack on firefighters' jobs and conditions, it is no wonder that there are growing calls for an alternative political option that backs the workers against the bosses and the political elite.
"RMT will be convening a conference this autumn to look at the options for a political alliance at the next election which challenges the cuts agenda of the three main parties and offers hope to the millions whose jobs are on the block in this race to the bottom."