Nick Clegg is set to warn that Britain's recovery remains "slow and fitful" ahead of the publication of key economic data.
The Deputy Prime Minister is to strike a cautious note despite expectations that the country will finally have emerged from recession when GDP figures are released later this week.
He will also fire a shot across Tory bows by insisting that a "balanced and engaged" approach to Europe is vital for the UK's prospects.
The intervention comes in a speech to financial services bosses at the CityUK annual dinner this evening.
Analysts have been predicting a 0.6% rise in GDP for the third quarter, potentially lifting the economy out of the longest double-dip recession since the Second World War.
The Olympics and a bounceback after the Diamond Jubilee bank holidays are thought to have helped drag the country out of the mire. The Liberal Democrat leader will boast that his party is a "sensible, centrist and pragmatic" influence in Government.
"Bluntly, with the economy still fragile, this is not the time for dogma," he will say. "There's a lot of speculation about what tomorrow's GDP figures will bring. Whatever they look like, we know that, overall, we've set the economy on the right path.
"But recovery is slow and fitful. Repairing the damage following the shock in 2008 is a gradual healing process. And the Government must remain absolutely focused on the reforms that will drive growth."
Foreign Secretary William Hague stepped up a Conservative drive on Monday to repatriate powers from Brussels, saying the British public's disillusionment with the EU was "the deepest it has ever been".
But Mr Clegg will promise to be "vigilant against knee-jerk or dogmatic responses to our economic challenges", adding: "We need a balanced, engaged approach to Europe - essential to the interests of the City."