Pedro Sanchez is poised to win the backing on Thursday of Spain's parliament for another term as prime minister, with the country divided over his decision to grant Catalan separatists an amnesty in exchange for their crucial support in a vote of confidence.

His Socialist party finished second in an inconclusive July general election but he is expected to be voted in with ease.

Sanchez has reached deals with several smaller parties to ensure he has the support of 179 MPs -- three more than the required absolute majority -- in favour of re-establishing his minority coalition government with hard-left party Sumar.

To win the backing of two Catalan separatist parties, he agreed to grant amnesty to hundreds of people facing legal action for their role in Catalonia's separatist movement over the past decade.

Among the beneficiaries is Carles Puigdemont, who headed the regional government of Catalonia when it staged a failed secession bid in 2017. 

The endeavour included a banned referendum followed by a short-lived declaration of independence that sparked Spain's worst political crisis in decades.

Puigdemont fled to Belgium shortly after the referendum to avoid prosecution, but an amnesty would allow him to return and potentially run for office.

Sanchez defended the amnesty on Wednesday at the start of a two-day parliamentary debate, arguing it was needed to "heal the wounds" opened by the wealthy northeastern region's independence push.

"We will guarantee the unity of Spain through dialogue and forgiveness," the 51-year-old added.

- 'Political corruption' -

Critics argue the amnesty is a self-serving measure to allow Sanchez to remain in power and accuse him of trampling on the rule of law and selling out the country.

"Adopting measures that go against the general interest in exchange of personal benefit is political corruption," the leader of the conservative Popular Party (PP), Alberto Nunez Feijoo, said during the debate in parliament.

The PP won the most seats in the July election but fell short of a majority and Feijoo unable to get backing from other parties to win his investiture vote in September. 

The leader of the far-right Vox party, Santiago Abascal, has gone further in his criticism of the amnesty deal, calling it a "coup d'etat" and saying there should be "no restraint" in the response to it.

Several polls show over half of all Spaniards oppose the amnesty.

In recent weeks, tens of thousands of people have joined street demonstrations backed by the right.

In a sign of the tensions, over 1,600 police will be deployed on Wednesday and Thursday for the parliamentary debate and vote, according to the interior ministry.

That is a similar deployment of officers that is used during football matches deemed "high risk".

Sanchez -- one of Europe's longest serving Socialist leaders -- also outlined some of his economic plans for his new term on Wednesday. 

These include making public transport free for young people and the unemployed, and continuing to link pension hikes to inflation.

But he will likely struggle to pass legislation since the various leftist and regional parties slated to back him on Thursday have radically different ideologies.

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