Rome (CNN) — The Italian parliament is expected to face a crucial vote on budget reform measures Tuesday, as the country’s prime minister comes under increasing pressure to resign amid unease over Italy’s economy.

Italy agreed to implement structural reforms during an European Union meeting in Brussels last month. Italian President Giorgio Napolitano said the reforms must be put in place or risk Italy’s credibility in the international community.

The budget vote comes after Prime Minister Silvio Berlusconi denied Monday’s rumors that he might resign.

But his main coalition partner added fuel to the fire Tuesday, telling reporters he had asked Berlusconi to take a sideways step.

Umberto Bossi, of the Northern League, suggested the prime minister should be replaced by former Justice Minister Angelino Alfano, although his office played down the remarks as not the “official line.”

Debate is due to get under way later on the budget reforms, with a vote expected Tuesday evening.

A press aide to Berlusconi also told CNN he had no plans to resign, and a message on the prime minister’s official Facebook page said: “The rumors of my resignation are groundless.”

But there are growing fears that Berlusconi’s government no longer has the strength to push through the austerity measures needed to get the economy back on track.

These include tax increases and raising the retirement age by two years, to 67.

A vote to pass the reform measures could give the embattled government enough fortitude to keep the prime minister in power.

Although Italy passed a package of austerity measures in September, including tax increases, some economists fear that without further reforms its debts could become overwhelming — and there would not be enough money in the European rescue fund to bail it out.

Italy has one of the largest bond markets in the world, worth an estimated 2 trillion euros (about US $2.8 trillion).

Experts say the recent lofty interest levels are particularly concerning because the European Central Bank has been buying Italian bonds since the start of August. The move initially pushed yields below 5% but that was short-lived.

Italian bond yields hit record highs Monday, getting perilously close to the 7% mark. The 7% level isn’t an automatic bailout trigger, but it is the level that prompted bailouts for Portugal and Ireland.

Many protesters over the weekend called for Berlusconi to step down, and said they want immediate elections. Others pushed for a technocratic transitional government to guide Italy through the difficult months to come.

Berlusconi said Friday at the G-20 economic summit that Italy had agreed to let the International Monetary Fund “certify” its reform program, a step designed to boost investor confidence.

International concern has focused on Italy — the third-largest economy in the eurozone — in recent weeks, amid concern that the financial crisis centered on Greece might spread. The ripple effects of a meltdown in Italy would be far more serious for the global economy than a collapse in Athens.

Although Italy’s economy is in much better shape than Greece’s, borrowing costs for the Italian government rose to a euro-area high of 6.43% Friday, adding to the pressure. The nation has debts equal to about 120% of its economic output.