Lord Pearson and UKIP want the UK to leave the EU
The leader of the UK Independence Party has said David Cameron winning a working majority in the election "is certainly the end of this country".
Lord Pearson said this was because the Conservative leader had ruled out a referendum on the UK's membership of the European Union (EU) for five years.
His comments came in an interview with the BBC's Straight Talk With Andrew Neil show to be shown at the weekend.
The Conservatives said a vote for UKIP "helps keep Gordon Brown in place".
"This election is a straight choice between five more years of Gordon Brown...or a Conservative government with David Cameron," said a Tory spokesman.
"[A Conservative government] which will change the law so that any future treaty that hands over areas of power will be put to the British people in a referendum, will never join the euro, and wants to bring back powers from Brussels to Britain."
Lord Pearson also named three Tory MPs against which UKIP will not stand.
The three Conservatives in question - Philip Davies, Douglas Carswell, and Philip Hollobone - are all well-known eurosceptics.
UKIP said last month it would not field candidates in seats held by MPs opposed to the UK's membership of the EU.
Lord Pearson told Straight Talk with Andrew Neil there would also be "at least one" Labour candidate it will not oppose.
He said the party would like to give a eurosceptic Liberal Democrat a free run - "if we can find one".
UKIP is due to announce next week the full list of candidates from the main three parties against which it will not stand.
Lord Pearson said UKIP may even offer its support to the eurosceptic candidates of other parties it doesn't stand against.
Returning to Mr Cameron's policy on a refendum, the UKIP leader said it was a "red herring".
He said that if the Conservatives win the election, Mr Cameron could more easily use the UK's membership of the Council of Europe to veto any more powers being passed to Brussels over the next five years.
On the immediate issue of the general election, Lord Pearson said UKIP's main aim was to see the party's former leader Nigel Farage elected in Buckingham.
Mr Farage is standing against the Speaker of the House of Commons, John Bercow.
Mr Bercow was previously a Conservative MP, but was criticised from within his party for being too left-wing.
• Straight Talk With Andrew Neil will be broadcast on the BBC News Channel on Saturday, 10 April at 0130BST, 0430BST, and 2230BST. It will also be shown on Sunday, 11 April at 0130BST and 2330BST, and on Tuesday 13 April at 0330BST.