By Holly Ellyatt & Stephen Sedgwick, CNBC

Greece’s last-ditch offer of new reforms might have raised a cheer on the markets Monday, but whether the measures will pass muster among the country’s creditors – let alone its own parliament and people — is another matter.

As Greece’s Prime Minister Alexis Tsipras flew into Brussels Monday to try to avert a debt default by his country, thousands of Greeks gathered in central Athens in rival camps to protest against austerity and a potential Greek exit of the euro zone.

Tsipras and his Syriza party, elected in January on their anti-austerity pledges, could now face a backlash within Greece for their new reform proposals to Greece’s lenders.

On Tuesday, Greece’s deputy speaker of parliament said Greek lawmakers could struggle to pass the reform program offered to lenders by Tsipras, telling Greek broadcaster Mega TV that he believed it would be “difficult to pass by us,” according to Reuters.

Killing the economy?

Adonis Georgiadis, a member of parliament (MP) for the Greek opposition party, New Democracy, told CNBC the reforms –based on higher taxation on businesses and the wealthy — would “kill the economy” and should not be accepted by Greece’s creditors, the so-called “troika” of the European Commission, European Central Bank (ECB) and International Monetary Fund (IMF).

“What he’s trying to do is exchange reforms for more taxes and the troika should never accept something like that. The philosophy of the memorandum (Greece’s bailout package) was to make our economy more competitive and be able to survive a loan in the real world but with all these taxes (proposed by Tsipras) will kill our economy,” he said.

Speaking to CNBC in Athens, Georgiadis said that the higher taxation would prompt Greece’s wealthy class to leave the country and would damage investment. “At the end of the day we’ll have less money….they (Syriza) cannot put us in a program that will destroy the economy for ever.”

Georgiadis was formerly health minister under the New Democracy government, which had a track record for cooperating more fully with lenders demands until it was ousted in snap elections in January. He told CNBC that, although he didn’t know if he would vote through the deal, he did not want to see Greece leave the euro zone – which could happen if the Greek parliament rejects the deal.

“Tsipras has put us in a very big dilemma,” he warned.

Worrying for Tsipras, the proposals don’t appear to have met with much more favor from within his own camp either. Syriza MP Costas Lapavitsas said that he was “deeply concerned” by the proposed reforms.

“I’m deeply troubled by what I read. It looks like we’ll be imposing a lot of taxes and okay, there will be some re-distributive aspect to the taxes, but they are new taxes and are designed to make a primary surplus and they are recessionary measures.”

He said he would “wait and see” what creditors said about reforms before deciding whether to approve the reform measures himself, or not. “I shall have to wait and see, I am skeptical about what the lenders say, I expected a hard response tomorrow (from lenders) and I expect new demands from them.”

Asked whether the measures could tear his party apart, Lapavitsas said he was “very worried” about the party’s future.

“If (the reforms) looks like this then I, and many other Syriza MPs, will have a lot of difficulty approving them…the Greek people voted us in because we opposed austerity and I’m very concerned about what this situation will do to our grass-roots support. There will be a lot of people who are very concerned and troubled about this situation.”

Hopes and protests in Athens

Hopes rose Monday that Greece will come to some kind of reforms-for-rescue deal with its international creditors this week after Athens presented an 11th-hour set of amended reform proposals Monday. 

The new set of measures were presented to euro zone finance ministers and leaders at a set of emergency summits in Brussels. The new plans showed Greece propose higher taxation on the wealthy and larger businesses, curbing early retirement and social security contributions but had not moved on pension and public sector wage cuts.

After discussing the proposals with fellow senior euro zone leaders, the President of the European Council, Donald Tusk, said the plans were a “positive step forward” and hopes of a deal rose.

But German Chancellor Angela Merkel struck a more cautious note, however, saying she couldn’t give “any guarantee” that an agreement would come. “There’s still a lot of work to be done,” she told reporters – a warning echoed by the head of the International Monetary Fund, Christine Lagarde.

The proposals are now expected to be discussed further on Wednesday at another evening meeting of the Eurogroup of euro zone finance ministers and then on Thursday, euro zone leaders will again review the plans and could then either endorse or reject the proposals.

Greece owes the IMF 1.6 billion euros on June 30 and could default on the debt without a last tranche of bailout aid worth 7.2 billion euros, although its disbursement is reliant on reforms. On Tuesday, AP reported that the ECB had increased the amount of emergency liquidity that Greek lenders can draw on, citing an unnamed banking official who declined to give an exact figure.

Game of penalties

Patrick Esteruelas, head of Sovereign Risk at Emso Partners, told CNBC Europe’s “Squawk Box” Tuesday that the current crunch point in negotiations were like a “football game that had reached penalties.”

“As we know, Germany always wins on penalties. At the last minute, Germany has extracted what is the best deal it could have expected from Greece but, make no mistake about it, this is not a particularly good deal for anyone involved. It’s going to be the basis of a compromise,” he told CNBC Tuesday.

Even if some kind of deal was reached, Esteruelas noted that the crisis would not be over for the country.

“It does look like it’s another potential giant kicking of the can down the road but saying that, I don’t think we should diminish the potential of a liquidity package to get us through the maturity humps of July and August (when Greece owes debts to European Central Bank and private bond holders).”