Blue Peter is being investigated by the Commission for Racial Equality (CRE) over the appointment of its latest presenter, Zoe Salmon.
Zoe Salmon was crowned Miss Northern Ireland in 1999
Ms Salmon - a former Miss Northern Ireland - joined the long-running BBC television show in 2004.
The CRE has received a complaint that the BBC practised racial discrimination by targeting people from Scotland and Northern Ireland for the role.
But a spokesman for the BBC said the post was advertised across the UK.
Ms Salmon, from Bangor, joined the show in October last year, and first appeared on screens in December.
She answered an anonymous advert in a local newspaper and did not even know she was applying for Blue Peter.
The advert for the presenter's job was placed in various Scottish and Northern Irish newspapers including The Scotsman and The Belfast Telegraph, as well as other national publications.
A spokesman for the Commission for Racial Equality confirmed they had received a letter of complaint from a member of the public.
He said: "We are looking at the matter and it will be dealt with in the usual way."
The BBC has rejected the claim, saying the search for a new presenter was "the widest recruitment ever undertaken" in BBC children's television.
A spokeswoman said: "In addition to adverts placed in The Stage and papers across the UK's nations and regions, we also approached agents and BBC Talent in a bid to cast the net as wide as possible.
"We viewed hundreds of tapes from candidates of all backgrounds, from across the whole UK."