I once heard a boy complain with so much exasperation,"why should I bother myself with the way I speak the English language, as far as my message is understood,then am good to go".I replied him by saying."English Language has gained a prestigious and an indispensable status more than any other language in the globe,therefore your good usage of it especially the spoken aspect is very sacrosanct if w must break new grounds in our new world order.That does not mean our native languages are not relevant,infact they are our identity and heritage(every code has its domain of usage)
Now,what is Mothertongue interference?MT interference is the involuntary influence of one language on the other.MT interference is not a voluntary action,this phenomenon is always dominant in a multilingual situation,therefore the reason why Nigerians find it difficult to speak the queens English is not far fetched,it is because our native languages(L1) have influenced our English phonetic make up.
Furthermore,some phonetic sounds that are present in English phonemic system are abscent in the phonemic system of our local languages.eg,the dental fricatives in (think,this,thus) and the vowels in(her,burn,hunt,father),There we resort to what is called "phonemic substitution".sometimes I wonder why the Ghanians tend to speak the Received pronunciation(RP)better than we Nigerians.
Another aspect that poses a problem to us is supra-segmentals which is also a branch of phonetics and phonology, by supra-segmentals I mean stress and intonation.We find this aspect challenging because English Language is stress timed while our African langues are tonal in nature.Right stress placement goes a long way in determing if a word is a noun or a verb.for example: REcord(noun)-reCORD(verB-)
In conclusion,we can improve our spoken English by undertaking the following measure;visiting phonetic sound laboratories,undertaking speech therapy,downloading audio pronunciation exercises(peter Roach)and lastly cultivating the habit of tuninig to BBC---------------Written by Daniel Egwahor,(BA)English and Literature ()2016

Studied all this in school, mother tongue interference is a bittch especially when you acquired the mother tongue before learning to speak English. but for those who mastered mother tongue and English simultaneously, the interference is barely noticeable.

Heromaniaa:
Studied all this in school, mother tongue interference is a bittch especially when you acquired the mother tongue before learning to speak English. but for those who mastered mother tongue and English simultaneously, the interference is barely noticeable.

I believe the basic essence of 'communication' is the ability of the second party to decode' what is being discussed.but that does not literarily mean that the queen's English should be jettisoned.

Nonetheless,mother's language interference in our speech as Africans is sacrosanct except the person was not born or breed here.

Even our professors of English are not exempted from this scourge.

If anyone can speak simple and correct English with meagre interference of the mother's tongue,that's acceptable for me.

Lalasticlala, what do you have to say?