Pedro Sánchez vows to fulfil his duties 'with conscience and honour' as he is sworn in as Spain's new prime minister

Former prime minister Mariano Rajoy forced out following corruption scandal

Mr Sanchez became the first Spanish prime minister to be sworn in without a bible or a crucifix (Getty)

Pedro Sánchez has been sworn in a Spain's new prime minister after Mariano Rajoy was ousted following a corruption scandal.

King Felipe swore in the Socialist Mr Sánchez in the royal residence in Madrid today, with Mr Rajoy in attendance.

Being an atheist, Mr Sánchez became the first prime minister to take the oath to protect the Spanish constitution without a bible or crucifix since the country transferred to democracy in 1977.

Mr Sánchez, 46, said he plans to see out the remaining two years of the parliamentary term, however his Socialist PSOE party only holds a quarter of seats in parliament.

Six other parties supported the new prime minister when he filed a no confidence motion to his predecessor after one of Mr Rajoy's conservative party's former treasurers was convicted of receiving bribes, money laundering and tax crimes, for which he was sentenced to 33 years in jail.

During the ceremony on Saturday, Mr Sánchez said he would fulfil his duties "with conscience and honour, with loyalty to the king, and to guard and have guarded the constitution as a fundamental state rule".

He is expected to reveal the members of his cabinet next week.

When Mr Rajoy entered congress for the last time this week he shook hands with Mr Sánchez and congratulated him on his win. He has become the first prime minister in modern Spanish history to be defeated by a vote of no confidence.

Spain's constitution states that any party presenting a no-confidence motion must be prepared to rule should the motion be passed and they have a parliamentary majority backing it.

Pedro Sánchez, a former basketball player and economist, suffered two election defeats in 2015 and 2016. However he returned to win the Socialist primary and in his latest political move became one of the most powerful people in Spain, even though he himself is not a member of parliament.

Some political commentators say the Socialist party's lack of parliamentary majority will make it difficult to get legislation passed.

It will add further uncertainty to Spain's political landscape, which has already seen tumultuous 12 months. In October the Catalan independence referendum was held in the autonomous region of Catalonia, however it was not recognised by the Spanish government.