Gordon Brown said yesterday that it would be a mistake to question Britain's EU membership at a time of global economic problems.
Recent financial turbulence was "a wake-up call" for every economy, the Prime Minister told an audience of business leaders.
He also urged the EU to focus on economic reform and to be open, flexible and outward-looking rather than protectionist.
Critics have questioned Brown's commitment to Europe, particularly after he arrived late last month in Portugal for the signing of the Lisbon Treaty, overhauling the EU's structures.
Britain was well placed to withstand the global financial turbulence expected this year because of low inflation and interest rates and record high employment, Brown said, adding public finances were "in a sustainable position".
Brown said the EU must act immediately to protect against financial turbulence. He plans to host a meeting this month with French President Nicolas Sarkozy, German Chancellor Angela Merkel and Italian Prime Minister Romano Prodi to discuss stability measures.
"What is clear is that at this time of global economic uncertainty, we should not be throwing into question, as some would, the stability of our relationship with Europe and even putting into question, as some would, our future membership of the EU - risking trade, business and jobs."
"I strongly believe that rather than retreating to the sidelines we must remain fully engaged in Europe so we can push forward the reforms that are essential for Europe's, and Britain's, economic future," he added.
His remarks were seen as a riposte to opposition Conservative leader David Cameron who on Sunday said he wanted Britain, rather than Brussels, to decide on its social and jobs policy and suggested a future Conservative government might try to reopen the Lisbon treaty even if every state had ratified it.Reuse content