* Reform to involve spending cuts worth 4 bln euros for 2013
* Opposition Socialists say won't play ball
* Budget to pass parliament vote
(Recasts with speech in parliament)
LISBON, Oct 30 (Reuters) - Portugal will present plans for a thorough reform of state institutions and spending to its international lenders early next year, its prime minister said on Tuesday.
The euro zone member is struggling to meet the fiscal goals agreed under its 78 billion euro EU/IMF bailout. Tax hikes due to come into effect next year to bring down the budget deficit have met with broad social and political opposition and prompted the country's lenders to request that Lisbon come up with alternatives if higher taxes do not raise revenues.
Premier Pedro Passos Coelho said state reforms were needed in addition to austerity measures if the country is to overcome its debt crisis.
``Our problem is not just budgetary. There is a consensus in the country that we need to have a general reform of the state if we want to solve the crisis,'' Passos Coelho told parliament as he presented his draft 2013 budget.
He called on the main opposition Socialists and on employers and labour unions to collaborate on state reform as some of the changes could require a two-thirds majority in parliament. He did not say what the reforms would be.
``This debate is in the interests not only of the government, but the country,'' he said, adding the government would present the guidelines of the reform plan to creditors after the next quarterly evaluation of the bailout, probably some time early next year.
The government has promised to present to its lenders proposed permanent spending cuts worth 4 billion euros for 2013-14. Passos Coelho said such deep cuts ``would not be possible without revising some functions and structures of the state.''
The opposition Socialists have warned that constant budget cuts threaten to undermine key areas of the country's welfare state developed since it returned to democracy in 1974 after decades of fascist dictatorship.
``This plan is nothing but an excuse for your failure ... the Socialists will not be your life buoy,'' Socialist leader Antonio Jose Seguro told parliament after the prime minister spoke. The Socialists have already said they will oppose the 2013 budget.
The European Commission has said it wants a backup plan for spending cuts in case revenues fall short in 2013.
Passos Coelho did not specify any concrete proposals but said the reform had to put an end to debt unsustainability fuelled by excessive spending, but without undermining the welfare state.
The reform may require constitutional changes, but that was ``not a pre-condition'', he said.
``We don't necessarily have to change the constitution, but we should not rule it out, we have to discuss it,'' he said.
The government has a comfortable majority to pass bills, but a constitutional amendment would require support from two thirds of lawmakers - which has to include the Socialists.
The debt crisis and austerity measures have fuelled the country's worst recession since the 1970s, undermining tax revenues. Next year's budget deficit goal of 4.5 percent of gross domestic product equals a gap of around 7.5 billion euros.
The International Monetary Fund warned earlier this month of growing risks to the deficit-reduction programme due to lower tax revenues, growing popular resistance to austerity and the likelihood that the country will remain in recession next year. ($1 = 0.7749 euros)
(Reporting By Filipe Alves and Andrei Khalip; Editing by Susan Fenton)