Catalonia's vice president has today said Spain has given the region's separatists no option but to proclaim a new republic.

Oriol Junqueras said his party - one of two in the ruling separatist Catalan coalition - is 'going to work toward building a republic, because we understand that there is a democratic mandate to establish such a republic.'

But Junqueras insisted he was speaking on behalf of his Republican Left party and not for the regional government of President Carles Puigdemont.

He said the Spanish government 'is giving us no other option.'

Oriol Junqueras (centre) is 'going to work toward building a republic, because we understand that there is a democratic mandate to establish such a republic'

His remarks come amid frantic jockeying in the Catalan government on how to respond to plans by Spanish authorities to fire them and directly manage the region's affairs.

It comes after a Catalan government spokeswoman said Catalonia's separatist leader Carles Puigdemont will not appear before the Spanish Senate in Madrid to state his case for independence.

'He will not go on Thursday or on Friday,' the spokeswoman explained, after the Senate suggested Puigdemont could appear at the upper house before it gives Madrid the green light to take over Catalonia's regional powers.

She did not give a reason but another Catalan government source said it was because Spain's central government 'has already announced that it will implement Article 155 (of the Spanish constitution) no matter what.'

On Wednesday, Spain's prime minister said his government's plans to take control of Catalonia's key affairs and halt the region's push for independence are 'exceptional'.

Prime Minister Mariano Rajoy told Parliament that invoking constitutional authority over Catalonia was the 'only possible' way to bring the region back in line with Spanish law, which he said the separatist Catalan government has violated repeatedly.

The Senate had suggested Puigdemont (pictured) could appear at the upper house before it gives Madrid the green light to take over Catalonia's regional powers

Rajoy said he hopes the measures planned, which includes removing Catalan government officials and curtailing the regional parliament's powers, will be brief.

They should end with a regional election he hopes to call soon, but only will be lifted once order is restored in Catalonia, the prime minister.

Spain's Senate, based in Madrid, is expected to approve the measures on Friday. Catalan President Carles Puigdemont was expected address the Senate to argue against them, but has chosen to stay in Barcelona.

Puigdemont instead plans to attend a session of the Catalan parliament in Barcelona, the region's capital, beginning Thursday and ending Friday, officials said. They spoke on condition of anonymity in keeping with internal party regulations.

Rajoy has asked the Senate to invoke a section of the Spain Constitution, Article 155, that allows the central government to step in when a region is found to be acting illegally. The action has never been taken before.

Prime Minister Mariano Rajoy (pictured) told Parliament that invoking constitutional authority over Catalonia was the 'only possible' way to bring the region back in line with Spanish law

He argues it is needed now to stop the Catalan government from acting on the results of an outlawed October 1 referendum that Puigdemont said gave him the mandate to declare independence.

'The government's response is the only one possible, given the stance of the Catalan institutions,' Rajoy said. 'I am fulfilling my duty and I am doing it in the face of a rejection of our laws, of our Constitution and of the millions of Catalan citizens who can see that their (regional) government has flouted the law.'

Rajoy said the aim of Article 155 is not to suspend Catalonia's self-government but 'to restore legality, boost the social co-existence that has been broken in Catalonia and tackle the economic consequences that its decisions are provoking.'

The uncertainty over Catalonia's future could have an economic impact. Credit ratings agency DBRS warned today that the situation is hurting the region's economy and could become a drag on Spain's economy.

Rajoy argues direct rule is necessary to stop the Catalan government from acting on the results of an outlawed October 1 referendum that Puigdemont said gave him the mandate to declare independence. Pictured: Catalan nationalists wave the region's flag on Saturday

The political turmoil brought by Catalonia's standoff with the national government 'is discouraging investment and tourism in the region,' DBRS said in a statement.

With Catalonia representing about one-fifth of Spain's annual gross domestic product, any slowdown in the region would affect the national economy.

The Spanish government has revised downwards its growth forecast for 2018 to 2.3 percent from 2.6 percent, largely because of doubts over Catalonia's future.

DBRS says the effects on the national economy will be 'manageable,' however, unless the crisis becomes protracted.