And they say it is absolutely essential that the People's Party-led government immediately produce accurate figures over the country's GDP as debt burdens weigh on hardworking families.
The average Spanish family is crippled with £118,000 (€136,000) in debt brought on by years of mismanagement, it has been warned.
But leading economist Robert Centeno says the unstable administration led by Rajoy which has been in gridlock since the controversial election in 2015 is not being honest about Spain's current economic conditions.
Prime Minister Mariano Rajoy is not being honest say critics
People don't really know what type of menace the national debt is for their lives
And there are growing calls for him to disclose figures amid serious concerns Spain could be set to default on loans which cannot conceivably be paid off for half a century.
Mr Centeno said: "People don't really know what type of menace the national debt is for their lives.
"The mass media in Spain simply certify the 'official' figures that the government gives.
Firefighters were on the streets following a demonstration in Barcelona
“The official debt is now at €1.1 trillion, but the debt is much higher.
"Let me say that only a miracle will reduce that amount of debt, but anyway, even in that improbable event, Spain would have to give to Brussels its real total amount national debt figures.
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"This total amount of debt which has nothing to do with the dossier we have sent to the European authorities is published every three months by the bank of Spain under the name of 'circulating passives'.
A demonstration against cuts in public education in Barcelona in early March
"And the last figure given by the Bank of Spain is €1.56 trillion.
"This is public debt. Debt generated from the central government, the autonomous communities, the local government and the social security.
"What I am trying to say is that the total figure of the National Spanish debt is a huge lie.
"You just have to do the figures".
Demonstrations turned ugly after Spanish students took to the streets
Mr Centeno says Spain is careering towards a third world economy.
In the space of just three decades Spain has dropped from being the 9th to the 14th largest economy in the world.
Mr Rajoy has been declared a 'persona non grata' of Pontevedra, his adopted city and is overrun with politicians, with the leader said to employ 2,500 special advisors as he continues to rule Spain with his minority government.
'Bloc’s big four' meeting at the Hall of Mirrors Tue, March 7, 2017
The best pictures from the Versailles Palace during a summit gathering heads of state and governments from France, Germany, Spain and Italy, in Versailles
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French President Francois Hollande welcomes German Chancellor Angela Merkel during arrivals for a Franco-German-Italian-Spanish summit ahead of the upcoming EU Summit in Versailles
Mr Centeno, added: "In Spain centralised spending is creating inefficiency and an extreme lack of control.
"A recent study shows that Spain has 445,568 politicians, including trade unionists, which is twice as many as Italy and France, or Germany with twice as many citizens as three times less political office.”