Image caption Humza Yousaf believes Jim Dempster should have been expelled by Labour

Scottish Labour has not contacted key witnesses in a racism investigation it began three months ago, the BBC has learned.

The party has yet to ask Transport Scotland officials for evidence in the case of a councillor who made controversial remarks about Transport Minister Humza Yousaf.

Mr Yousaf said Labour's promise of swift action appeared to "ring hollow".

Scottish Labour said investigations were continuing.

It is understood the investigation is still at a "preliminary" stage.

In March, Dumfries and Galloway councillor Jim Dempster was suspended by Labour following a complaint.

He had apparently told transport officials that "no-one would have seen (Mr Yousaf) under his burka" when he visited the area.

The councillor apologised and said he was "ashamed and embarrassed". But Mr Yousaf said he should be expelled by Labour.

Image caption Richard Leonard told an anti-racism rally that "we need to be impatient and angry in our pursuit of justice and equality"

The party leader, Richard Leonard, ordered an investigation. But almost three months later, Transport Scotland said there had been "no contact at all" from Labour.

In an interview with BBC Radio's Good Morning Scotland programme, Humza Yousaf said: "I was told there would be a swift investigation - I've not heard anything.

"I was heartened a few weeks after the complaint that I made, when Richard Leonard said there would be a zero tolerance approach and he'd be personally accountable for that.

"Almost three months later, for nothing to have happened, his words really ring hollow".

Diversity training

It is understood the case is to be considered by Labour's ruling body - the NEC - next month. The party said it would inappropriate to comment.

It's not the only racism case under investigation.

In January, the Labour MSP Anas Sarwar said the party's council group leader in South Lanarkshire had told him "Scotland wouldn't vote for a brown, Muslim, Paki".

The councillor - Davie McLachlan - categorically denied making the remarks but was suspended by the party.

It's understood this case has been referred to UK Labour's national constitutional committee for a hearing later this year.

In February, the MP Hugh Gaffney apologised for making what he said were "deeply offensive and unacceptable" remarks about Chinese and LGBT people.

He was reprimanded by the party and sent for diversity training.

In March, when Councillor Dempster's case was made public it led to further allegations against him.

A Sanquhar man of Pakistani origin told the BBC that he had been repeatedly racially abused by Jim Dempster before he was elected. Councillor Dempster has strongly denied that allegation.

Around this time, Scottish Labour leader Richard Leonard told an anti-racism rally that "we need to be impatient and angry in our pursuit of justice and equality".

Letter of complaint

A Scottish Labour spokesperson said: "Investigations into alleged misconduct are continuing and as a result it would be inappropriate to comment further at this time."

In May, five members in the Glasgow south-west constituency said they felt "not wanted and not welcome" in the Labour party because of their Asian background.

They made the complaint in a letter to the party leadership and it's understood they have been invited to discuss their concerns with Mr Leonard after Ramadan.

Scottish Labour adopted a plan to tackle racism at its Dundee conference in the spring and Mr Sarwar has established a cross-party group at Holyrood to tackle Islamophobia.