David Cameron is to warn European leaders he will "think again" about the UK staying in the EU if his demands for reform are "met with a deaf ear".
The PM will deliver his warning on Tuesday to coincide with a letter to the European Council president setting out the changes he wants for the UK.
The letter to Donald Tusk will mark the start of the UK's formal re-negotiation of its EU membership.
Former Labour MP Austin Mitchell accused Mr Cameron of bluffing.
The Conservatives have promised an in-out referendum on the EU by 2017.
In a speech on Tuesday, Mr Cameron will say: "If we can't reach such an agreement [on reforms], and if Britain's concerns were to be met with a deaf ear, which I do not believe will happen, then we will have to think again about whether this European Union is right for us.
Heart and Soul
He won't pull out; he will want to stay in because all the vested interests say they want to stay in
Austin Mitchell, Labour MP
"As I have said before - I rule nothing out."
Mr Cameron will say he is ready to campaign to stay in the EU "with all my heart and all my soul", but only if the terms are right.
He has already said he wants an end to the commitment to ever-closer union, more power for national governments and restrictions on benefits for EU migrants.
The speech will be Mr Cameron's strongest warning yet that he is prepared to consider life outside the EU if he doesn't get what he wants, BBC political correspondent Carole Walker said.
Mr Cameron will also insist he has "every confidence" that it is possible for the negotiations to deliver an agreement which works for both the UK and the EU's 28 other nations.
"Those who believe we should stay in the EU at all costs need to explain why Britain should accept the status quo. I am clear that there are real problems with this," he will add.
But he will also say there are some "economic risks" to staying in the union and he will cite examples such as EU regulations which "hold back our ability to trade and create jobs".
‘Significant risks’
“And there are also significant risks if we allow our sovereignty to be eroded by ever closer union, or sit by and do nothing about the unsustainable rate of migration into our country," he will say.
Eurosceptic Mr Mitchell told the BBC he thought the PM's comments were really "just a game of bluff".
"He's going to now pretend that, oh yes if we don't get our way we should pull out, and you've got to be nice to us but he doesn't really mean it," he said.
"He won't pull out, he will want to stay in because all the vested interests say they want to stay in... and I think Cameron himself is a strong pro-European."
Latest Stories
-
Police arrest four suspected robbers, kill one in separate operation in Ashanti region
1 minute -
Mugabe Saifu Maase appointed board member of TOR
7 minutes -
GoldBoard committed to exporting gold from legal sources – Lands Minister
15 minutes -
New board inaugurated to revitalise Tema Oil Refinery
23 minutes -
Britain’s immigration reset and its ripple effects on Ghana-UK migration
28 minutes -
Arthur vs Ameyaw: Strikers set for showdown in UG Corporate Football League final
34 minutes -
NGIS Money Market Fund posts strong financials despite dip in investment income
45 minutes -
Blue Water initiative to focus on de-chemicalising rivers – Lands Minister
52 minutes -
NSMQ 2025: Osei Kyeretwie SHS students sacked from quiz hall for disobeying quiz mistress
57 minutes -
Lands Minister: Azumah Resources, E&P close to agreement on mining lease
1 hour -
Sammy Flex reacts as Shatta Wale restructures management
1 hour -
Power consumers urged to engage certified electricians before applying for meters
1 hour -
NGIS Anidaso Mutual Fund shares record 13.26% year-to-date yield
1 hour -
MDF explores local poultry feed production to boost food security – Lands Minister
1 hour -
1,345 galamsey suspects arrested since January 2025 – Lands Minister
2 hours