Madrid's culture minister Inigo Mendez de Vigo has accused the secessionist coalition ruling the northeastern region of bending the laws to go ahead with a vote regardless of warnings from courts and a suspension by the country's Constitutional Court earlier this month.
There will not be a referendum on Catalonia's independence on Sunday, the cabinet spokesman for Spain's government said as the vice-president of the region predicted the majority of eligible voters would turn out.
Catalan authorities say they will declare independence within 48 hours after announcing the vote's results if the yes side wins.
The Spanish government has fought the referendum with a myriad of legal actions criticised by many in Catalonia.
"The government has a constitutional mandate to enforce the laws maintaining civic order," Mr Mendez de Vigo said on Friday during a regular weekly press briefing.
"Nobody is above the laws and whoever violates them will face consequences."
However, Catalonia's vice-president said more than six out of 10 voters are expected to take part in the poll despite the crackdown from Madrid.
Oriol Junqueras said Catalan citizens will be able to vote "even if somebody takes voting stations by assault and tries to avoid something as natural as placing a voting slip in a ballot".
Spain's Constitution says only the nation's government can call a referendum on sovereignty.
Police forces acting on judges' orders have seized ballots and arrested regional officials in the crackdown.
Mr Junqueras said an internal poll showed more than 60% of the 5.3 million eligible voters plan to cast ballots.
He displayed a prototype of the plastic ballot boxes planned for more than 2,300 voting stations.
Far-reaching effects of the referendum could see Barcelona come and play in the Premier League if Sunday's referendum on Catalan independence is passed, the region's sports minister has claimed.
Among the many uncertainties is what will happen to the region's football clubs, including FC Barcelona , if Catalonia becomes a new country.
Gerard Figueras, Catalonia's minster of sport, said: “In the case of independence, Catalan teams in La Liga – Barcelona, Espanyol and Girona – will have to decide where they want to play: in the Spanish league or a neighbouring country: Italy, France or the Premier League.
“Now in Spain there are teams from other countries who play in national leagues: clubs from Andorra in football and basketball. Monaco play in France, in England Welsh clubs. I don't think that UEFA has anything against seeing another club play in a different league from their country.”
Spain have insisted Barcelona will not be allowed to play in La Liga if the illegal vote goes through.
A recent statement from Barcelona said: “FC Barcelona, in holding the utmost respect for its diverse body of members, will continue to support the will of the majority of Catalan people, and will do so in a civil, peaceful, and exemplary way.”
