Greece's prime minister is to meet with ministers Monday as he tries to get new austerity plans through Parliament despite increasing dissent within his own party and big demonstrations in the country's two largest cities.

The austerity plans - remedial measures this year and a package through 2015 - are required if Greece is to carry on getting money from last year's €110-billion package of rescue loans from the International Monetary Fund and other countries that use the euro. Greece looks like it will need more money to cover a funding gap next year and prevent the country from defaulting on its debts.

Last week, debt monitors from the EU and IMF said Greece should receive the next €12-billion instalment of the bailout in early July - as long as additional austerity and privatization measures are deemed sufficient. A final decision is to be taken by the IMF board and the euro group in meetings later this month.

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Prime Minister George Papandreou's talks at an informal Cabinet meeting Monday afternoon will be the first of a series of meetings. On Tuesday, he presents the plans to his governing Socialist party deputies before the Cabinet reconvenes on Wednesday to send the measures to Parliament.

But the extra austerity - which includes €6.4-billion worth of remedial measures for this year and a midterm program that will run from 2012-2015, two years beyond the current government's mandate - has disgruntled even members of the governing PASOK party, which only has a majority of six in the 300 member Parliament.

Last week, 16 PASOK deputies signed a letter demanding an extensive debate on the measures before they are ratified, while one of the signatories threatened not to vote for the reforms otherwise.

"If the draft legislation is brought to Parliament without prior discussion, I will not vote for it," Thomas Robopoulos told state TV on Friday.

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The measures will include tax increases, spending cuts and trimming the size of the bloated public sector. The government is also pushing through an ambitious €50-billion privatization program.

The ever increasing cutbacks have also led to a public backlash, with tens of thousands of Greeks flooding into the main squares of cities across the country in a protest fuelled by appeals on social media and now in its second week.

Sunday, the 12th straight day of protests modelled on similar demonstrations held in Spain last month, saw the largest gatherings so far. More than 60,000 people jammed the capital's main Syntagma Square, according to police estimates, although protesters claimed the numbers were much higher. Another estimated 20,000 people rallied in the second largest city of Thessaloniki in the north.

With no particular political affiliation, the rallies have been a break from the traditional form of demonstrations in Greece, which are usually organized by trade unions or political parties and often turn violent. So far, there has been no violence in the rallies in Athens, although there was a minor scuffle in Thessaloniki.

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Protesters are expected to gather again in Syntagma Square on Monday night. Metro workers scheduled a strike for Monday to finish at 4 p.m. so protesters could get to the capital's centre in time for the rally, set to begin at 6 p.m.