Political parties and Corruption

Political parties and Corruption:
Can we say its different kind of corruption by political parties?
After elections opposit parties become friends and share the govt .
In every election there are 5 or 10 or less or more candidates stand for elections few belong to political parties like bjp ,congress and others and few are independant candidates.

when we vote to someone,we consider that to which political party a candidate belongs, and then we vote for him. sometimes some people do not like him,but still vote for him because he is candidate of party which he likes and in which party he belives.
But after elections we see that the parties who fought elections against each other have become friends, forgot there policies there agenda,there oppostion for each other and they formulate goverment only to form the governemnt.
i think we need a new law that only highest election sits winning party should form the governemnt with help of others but other parties should not be given any kind of place in the governemnt they can support this party ,just to save the expenses of another election, or they can support this party on cause basis. without participating or sharing the government.
Today what is happening is that,once party wins hightest sits in election,
that party just to formulate the govt starts to purchase other smaller parties ,independant candidates by offering them ministries or somekind of
gift.
is this not one kind of corruption to form the government ,the party is giving gifts to others in form of place in government or offering them
ministries,makeing them cabinet minister etc.
when some company want loan from bank, if bank manager demands or receives a gold ring or job for his son in that company to give loan to that company,this bank manager becomes criminal it is called as courruption.
same way to formulate govt,the party offers cabinet ministry ?
what is your opinion ?