The SNP’s depute leader has backed Humza Yousaf’s decision not to suspend the whip from Nicola Sturgeon, saying it is in the interests of “natural justice” that she stays in the party.

Keith Brown said other cases where the party’s MSPs had been suspended while allegations around them were being investigated involved “different circumstances”.

At the weekend Ms Sturgeon became the third figure in the SNP to be arrested and interviewed by detectives in the ongoing investigation into the party’s finances.

Like former chief executive Peter Murrell – Ms Sturgeon’s husband – and former treasurer Colin Beattie, she was released without charge pending further investigation.

On Tuesday, Mr Brown told the BBC’s Good Morning Scotland programme that he “certainly” agreed with Mr Yousaf’s decision not to suspend his predecessor as the investigation is ongoing.

He said: “I think it’s in the interest of natural justice, which is the principle which Hamza, the First Minister, is following.”

SNP MSP Michelle Thomson was among those calling for Ms Sturgeon to resign from the whip while the investigation was ongoing.

Ms Thomson argued that she herself had needed to resign the whip while an MP in 2015, despite not being “personally under investigation” and “certainly not arrested”.

Former leadership contender Ash Regan and MP Angus MacNeil, both of whom were critics of Ms Sturgeon’s leadership, had also suggested that she should be suspended.

Mr Brown said Ms Thomson took the decision to remove herself from the SNP group at Westminster.

He said: “There are different circumstances in each of these situations.

“I accept that and that’s bound to be the case, but in relation to the current case, Nicola Sturgeon has not been charged – she has not been accused, in fact, of anything.

“The arrest I appreciate is a dramatic thing to have happened.

“It’s perhaps not as well understood that arrest is just a way of making sure that the interview and information gathering by the police is put into formal footing.”

He also raised the case of Boris Johnson, saying Conservatives had not called for him to be suspended despite being investigated by the police.

The SNP depute leader said Ms Sturgeon had given a “strong defence” of her own innocence and he was not aware of any complaints being made to the party’s member conduct committee.

The Scottish Conservatives said some of Mr Brown’s claims were “absurd”.

Deputy leader Meghan Gallacher said: “Keith Brown’s desperate spinning in defence of Humza Yousaf will only pour petrol on the bitter civil war between SNP MSPs and MPs over Nicola Sturgeon’s preferential treatment.

“His claim that Michelle Thomson had voluntarily given up the SNP whip when she was under investigation amounts to gaslighting, as she has said very clearly she had the whip removed from her by Nicola Sturgeon.”

She added: “No amount of spin can disguise the fact that Humza Yousaf is so compromised by his closeness to Nicola Sturgeon that he is having to move the goalposts on internal discipline.”