Thousands of people marched throughout the streets of Lisbon on Tuesday (November 26) as Portugal's parliament gears up to vote on an austere 2014 budget, almost certainly triggering a spree of constitutional challenges that may threaten its smooth exit from an international bailout next year.

The Constitutional Court has already overturned a series of previous public spending cuts. Opposition parties have said they will challenge new ones once the budget is passed.

The threat could force the government to seek alternative measures, most likely tax hikes. The danger is that that could undermine an economy just recovering from its worst downturn since the 1970s.

The 'troika' of lenders in Portugal's bailout - the European Commission, the International Monetary Fund and the European Central Bank - have also identified challenges by the court as potentially the biggest threat to Lisbon's efforts to meet budget goals and to exit the bailout next year.

The problem is that the scale of the measures that could be challenged, both those included in the budget and other plans, amounts to more than 1 billion euros. A previous law to increase public employees' working hours is also pending a decision by the court.

The government has repeatedly said its overriding priority is to meet budget goals as the best way to regain the necessary confidence to exit the bailout as planned in June 2014 and return to financing itself in debt markets. In 2014, the government needs to cut the budget deficit to 4 percent of gross domestic product from 5.5 percent this year.

Presented by Adam Justice