Ukip will form an electoral pact with Northern Irish MPs to keep the Tories in power after the next election, Nigel Farage said this morning.

The Ukip leader said the Conservative Party will emerge from the general election as the largest party but wouldn't have enough MPs to govern on their own.

Mr Farage said he would force an early referendum on Britain's membership of the EU as his price for keeping David Cameron in Number 10.

Ukip leader Nigel Farage said the Conservative Party will emerge from the general election as the largest party but wouldn't have enough MPs to govern on their own

The Ukip leader's intervention comes amid growing pressure on the Tories to rule out a power-sharing deal with Ukip after the election.

Mr Cameron has repeatedly challenged Labour to reject a coalition with the SNP, but has side-stepped questions about whether the Conservatives would rely on Ukip to form a government.

But Mr Farage said this morning said he would not have a choice. He said: 'At the end of the day, this is all about numbers, isn't it?'

He added: 'I mean I still believe that the Conservatives will be the biggest party – not least of which is because Alex Salmond's party is doing so well in Scotland.

'I think between UKIP and possibly the DUP in Northern Ireland as well, there will be a body of MPs there to have significant influence and to force a referendum on our EU membership.'

Mr Farage has previously insisted he would be willing to support a Tory minority government only if a referendum on Britain leaving the EU was held before the end of this year – two years earlier than David Cameron plans.

Nigel Farage said Ukip would form an electoral pact with Northern Irish MPs to keep the Tories in power after the next election

The Tories have insisted that Mr Cameron needs two years to re-negotiate Britain's membership of the EU.

But Mr Cameron said: 'Donald Tusk and Mr Juncker, the two bosses of the European Union, have made it perfectly clear there is no renegotiation.

'When it comes to the fundamental point of the free movement of people and immigration into the UK, which is the number one issue in British politics and I think between now and May 7 will start to dominate this General Election campaign, there is no renegotiation.'

David Cameron may be forced to rely on Ukip and DUP MPs to stay as Prime Minister

Mr Tusk – the European Council president – last week claimed Mr Cameron's proposal for a new EU treaty was 'Mission Impossible'.

But the Prime Minister, speaking in Brussels on Friday, said a Tory victory in the General Election would give him a 'very powerful mandate' to win sweeping reforms and insisted it was possible.

He added: 'Tom Cruise normally prevails in the end. He's a little bit smaller than me, but I hope to be just as effective.'

But Mr Cameron has refused to rule out a coalition with Ukip, telling MailOnline: 'I don't want to have a coalition with anybody.

'I'm fighting for a majority government, there are 93 days to go and I'm not going to speculate about any outcome other than victory.'

Last week the Chancellor George Osborne demanded that Labour say it would not form a coalition with the SNP, who are expected to make big gains in Scotland.

But he refused to make the same promise about a Tory-Ukip tie-up.

Appearing on BBC One's Andrew Marr show, Mr Osborne said: 'It's just total nonsense, voting for Nigel Farage makes Ed Miliband the likely Prime Minister and it means instead of getting the referendum on Europe we get no referendum at all, so that's what a vote for Ukip is about and it's a fundamentally different situation from the SNP, you were asking Ed Balls about it, he again refused to rule out a deal with the SNP.

'We are fighting for a majority, we only need 23 more seats to get that majority.

'Nigel Farage and indeed Ed Balls are trying to muddy the waters, it's a fundamentally different situation for this reason - Nigel Farage is not going to win seats in the House of Commons, even on his own boasts he's only going to win a small handful.

'The SNP are likely to win dozens of seats because of the collapse of the Labour party, Ed Miliband can't be Prime Minister without the support of Alex Salmond and that creates an alliance between those who want to bankrupt the country and those who want to break up the country.'

Nigel Farage said Ukip MPs could join forces with DUP members, led by Nigel Dodds (left), in the Commons to keep David Cameron in Number 10

Mr Farage has claimed that his party will win a 'handful' of seats at the election, which means the Tories would likely also need the support of Northern Ireland's Democratic Unionist Party (DUP) to maintain a minority government.

Ukip would back the Tories' first budget if a referendum on Britain's EU membership was promised before the end of 2015.

Up until now, the Prime Minister has vowed to hold a referendum by the end of 2017, and has said he will campaign to stay in a reformed EU.