Labour officials involved in the controversial selection of Shabana Mahmood as the party’s candidate in Ladywood are to receive a grilling from an internal inquiry set up to investigate claims that the process was unfair.

The inquiry, announced in July, still has “a month or longer” to run, a Labour official said.

It is looking into claims that Ms Mahmood’s selection earlier in the year was marred by postal voting irregularities.

As many as 30 people said they were prevented by officials from voting for Birmingham city councillor Yvonne Mosquito on the grounds that they had not been members of the local Labour Party for long enough.

Sitting MP Clare Short, the former Labour cabinet minister who now sits in the Commons as an independent, is standing down at the next election, giving the Labour candidate a clear run at what should be a safe seat for Gordon Brown’s party.

Ms Mahmood, who is the daughter of Mahmood Ahmed, the chairman of Birmingham Labour Party, won the selection contest by 118 votes against 99 for Coun Mosquito.

But the result angered black church leaders, with Bishop Joe Aldred, chairman of the Council of Black-Led Churches, writing to the Labour Party to claim that some party members were excluded from voting.

A sub-committee of Labour’s National Executive Committee, the NEC Organisation Committee, is examining the selection process.

It is chaired by Amicus official and NEC member Mike Griffiths. Members include Keith Vaz, the Leicester East MP and former Minister for Europe.

The committee has yet to interview a number of those involved in the selection process. Labour is not naming those who have been summoned for interrogation, although they are likely to include Ian Riley, regional director for the Labour Party in the West Midlands.