Question

main function of opposite party

Answer 1

One function is to look after the flaws(mistake) of other party and to raise voice against it
M not sure its main or not but ya its one function for sure in order to suppress the other party.....
And increase their influence

Answer 2

The Opposition’s main role is to question the government of the day and hold them accountable to the public.The Opposition is equally responsible in upholding the best interests of the people of the country. They have to ensure that the Government does not take any steps , which might have negative implications on the people of the country. 

the role of the opposition in parliarment is basically to check the excessess of the ruling or dominant party, and not to be totally antagonistic. There are actions of the ruling party which may be beneficial to the massess and oppositions are expected to support such things.