The case hit the headlines last week after police arrested several people in connection with a kickbacks scandal involving the sale of masks during the pandemic.

One of those arrested was a close adviser to José Luis Ábalos, who served as transport minister between 2018-2021 and has been a key member of Sánchez’s Socialist party.

Although Ábalos was not implicated in the scandal, the Socialist party urged him to stand down as a lawmaker within 24 hours to take “political responsibility” for the scandal on his watch.

The aide, Koldo García, is suspected of pocketing commission on the sale of masks to the public authorities at the start of the pandemic in spring 2020.

READ MORE: What is the Spain’s ‘Caso Koldo’ corruption case all about?

But Ábalos refused to resign, telling reporters on Tuesday such a move could be seen as “an admission of guilt” even though he had “not been accused of anything”.

Keen to distance itself from a potentially explosive political story, the Socialists immediately said they were suspending him as a first step to expelling him from the party.

Ábalos will retain his seat by joining the so-called mixed group of lawmakers.

But his departure will leave the Socialists with just 120 of parliament’s 350 seats.

If he had resigned as a lawmaker, the party could have reappointed another deputy in his place, thereby hanging onto his seat — which would have helped Sánchez, whose minority coalition government is propped up by a very fragile support network.

It is a sensitive case for the party as Ábalos was part of Sanchez’s inner circle for years and one of a small band of supporters who remained loyal when he was briefly ousted as party leader in 2016 following bad election results.

Re-elected the following year, Sánchez made Ábalos the party’s number three.

And when Sánchez became premier in 2018, he brought Ábalos into the cabinet.

The aide is accused of using his position at the transport ministry to broker multi-million-euro contracts for the sale of masks with a firm that paid him commission.

With the money, he bought three apartments in the southeastern resort of Benidorm, one in the name of his two-year-old daughter, prosecutors say.