LISBON (Reuters) - Portugal's Prime Minister dismissed on Wednesday increasingly strident calls for an end to its austerity program, saying the country needed to ensure its European partners' support in regaining access to debt markets.

Pedro Passos Coelho spoke in the first parliamentary debate since the main opposition Socialists last week demanded that the government abandon its austerity drive, and after rallies on Saturday where hundreds of thousands of protesters called on the center-right government to resign.

"It is only possible to have our partners ready to help us in returning to debt markets as long as we are successful in executing the bailout program in a credible way," he told parliament. "We need to proceed with firmness and resilience."

The government has recently said it may seek an easing of its budget deficit targets under the EU/IMF bailout after a worse than expected economic performance in the fourth quarter of 2012.

Passos Coelho said Tuesday's statement by European Union finance ministers regarding smoothing out the debt redemption profiles for Lisbon's and Dublin's bailouts was favorable to Portugal's efforts to regaining market access.

Despite the Socialists' demands, the center-right ruling coalition has a comfortable majority in parliament and Passos Coelho said the government was fully capable of preserving political stability.

"Our partners who now support us can always count on the government to provide the political stability necessary for the country to preserve what it has achieved (under the bailout)," he said.

(Reporting By Andrei Khalip, editing by Axel Bugge, John Stonestreet)