Gordon Brown will warn Britain's European Union partners that he will not agree to any further "navel-gazing" internal reforms once the 27-nation bloc has approved a new governing treaty.
In Lisbon today, at his first EU summit since becoming Prime Minister, Mr Brown will tell his counterparts to end their long debate about EU institutions and start addressing issues such as job creation and climate change which matter to ordinary people.
Mr Brown will sign up to the new treaty tonight, which will streamline the EU's decision-making procedures, provided that Britain's much-vaunted "red lines" are preserved. These are designed to safeguard Britain's right to decide its own social and labour laws; common law, police and judicial processes; foreign and defence policies and tax and social security systems.
One minister said: "We will draw a line in the sand and say 'thus far, no further'. The treaty is needed but the EU will never win the support of its citizens if it embarks on yet another round of institutional reform."
Mr Brown hopes his stance will reassure any British voters who are worried that he is ready to approve the treaty without calling the referendum that Labour promised on its forerunner, the EU constitution which was scuppered by "no" votes in the Netherlands and France two years ago.
Mr Brown has come under mounting pressure from some Labour MPs, the Tory Opposition and Britain's Eurosceptic newspapers to call a referendum but argues that the treaty is a scaled-down version of the original blueprint and does not warrant one.
The Government has attacked as "myths" claims that the treaty will continue the drift to an EU superstate. But its critics have dismissed the "red lines" as a "red herring" designed to allow Mr Brown to claim victory.
A Labour-dominated Commons committee has also cast doubt on whether the safeguards won by ministers are watertight, and warned that Britain could face unlimited "fines" if it does not opt in to a common justice and home affairs policy in five years.
The Prime Minister will urge the EU to "move on" to issues such as how Europe should compete in the global economy – an issue already due to be discussed at the summit tomorrow in a recognition that the union needs to end its introspective debate.
But Mr Brown's free-market vision for the EU could cause tensions with Nicolas Sarkozy, the French President, who clashed with Britain at the last European summit in June over the wording in the treaty on competition. M. Sarkozy asked then: "What has competition ever done for us?"
The two leaders may also clash over Mr Brown's call for an end to the EU's internal debates. M. Sarkozy wants the EU to set up a "committee of wise men" to consider its long-term structure.
In a letter to fellow EU leaders before today's meeting, Mr Brown called for an "open and flexible Europe" that should "promote free trade and openness" – a firm rejection of demands for protectionist measures to safeguard European industries.
The Prime Minister said the EU was at a "critical juncture" as, for the first time in its history, it had an opportunity to become a genuinely global player. But he added: "This is the right time to bring to an end to this prolonged period of inward-looking institutional debate and focus all our efforts on the issues that matter most to the future well-being of the people of Europe – economic growth, jobs, the environment and security."
In the Commons, Mr Brown came under fire over the Government's U-turn on a referendum. David Cameron, the Tory leader, said the treaty was widely recognised to be the same as the constitution. "Why don't you admit the reason you won't have a referendum is that you are scared of losing it?" he asked the Prime Minister. "If you break your promise on this, no one will trust you on anything else."
Mr Brown replied: "It is an amending treaty. That is not fundamental change. We have managed to negotiate red lines in Europe which mean the national interest is protected."
Jose Manuel Barroso, the president of the European Commission, urged Britain, Italy and Poland not to prevent agreement at the summit, saying: "I hope this will not be the battle of Lisbon. We have a very good agreement on the table, the best on offer."
The Polish Prime Minister, Jaroslaw Kaczynski, is keen to push for stronger powers for his country, notably more voting clout in the Council of Ministers.
Italy's Prime Minister, Romano Prodi, who fears a decline of Rome's influence in the EU, is demanding that his nation keep a similar number of seats in the European Parliament compared to other big member states.
Summit on schedule
Noon: Gordon Brown will speak to European socialist parties in Lisbon before the summit at the Atlantico Pavilion
PM: Jose Socrates, the Portuguese Prime Minister and president of the EU, will open the summit
* 4 pm: Gordon Brown will welcome the draft of the treaty agreed by foreign ministers on Monday, saying it preserves the "red lines" for Britain on a fundamental charter of rights, foreign policy, security and home affairs issues
After 4 pm: Formal session will begin. It could go over into Friday, but there is agreement on the package. There will be a declaration on globalisation
Evening: A working dinner, which is broadcast to note-takers in a neighbouring room
Friday: Final agreement expected on amended treaty and likely discussion of the next summit agenda