A jailed Catalan separatist leader standing in Spain's national election this month has said he expected Prime Minister Pedro Sánchez to consider a possible referendum on the region's independence to help secure a second term in office.

In a news conference from the Madrid prison where he is being held, Jordi Sànchez - his party's top candidate in the 28 April ballot - suggested the likely need for coalition deals would spur his namesake to co-operate.

Mr Sánchez is standing trial for sedition for his role in a failed independence bid in 2017, and the wealthy region's undimmed ambition to split from Spain is among the most emotive campaign issues in the election.

Pedro Sanchez's Socialists are expected to win the most seats, but will need support from one or more other party - possibly including the Catalan separatists - to form a parliamentary majority.

He has taken a more conciliatory tone towards political dialogue with Catalonia than his conservative predecessor.

However, along with other mainstream leaders in Madrid, he has consistently rejected the idea of an independence referendum or any unilateral secession bid, and hardened his position as the election campaign has heated up.

Jordi Sànchez made his address from prison

In an interview with radio station Onda Cero given after the Catalan leader's comments, he reiterated that there would be "no referendum, no independence" for the region.

Jordi Sànchez, a member of exiled former Catalan leader Carles Puigdemont's PDeCAT party, said he thought political circumstances might persuade the outgoing prime minister – to whom he is not related - to have a rethink.

The secessionist movement would act on "the will that the citizens express themselves democratically at the ballot box, and we are convinced that sooner or later the Spanish Socialist party will accept this way," Mr Sanchez said.

Speaking to reporters via a video conference organised by the national news agency EFE, he said any other decision would "lead either to a permanent blockage (of the Catalonia independence debate) or pave the way for a government of the right".

Opposition to Catalan independence has been a core rallying cry for the conservative People's Party, centre-right Ciudadanos and far-right Vox, which could potentially win enough seats combined to form a viable coalition.

Jordi Sànchez and three other jailed Catalan politicians said last week the separatists should be more flexible about entering negotiations with Madrid, provided a vote on independence remained an option.

During today's news conference, he spoke mainly Catalan and sat in front of two symbols of Spanish unity: the red and yellow flag and a portrait of King Felipe.