Parliamentarians represent their party or the parliament?

I have been thinking of the actions of the PM in which he clearly sought to be useful to his party at the expense of his country. I am referring to his decision to accept a lot of nonsense from ministers from the UPA alliance parties, only to prevent the UPA coalition from disintegrating and thus being of use to his party i.e. Congress. He is on record to mention 'coalitional dharma/politics'.
Was he right? Why fault him for being of use to his party? After all, he was put on this chair by his party!
No, he was wrong to have done what he did. Once placed on the PMs chair, he no longer represented the party. He only represented the nation.
In this debate, I'd like to quote Right Hon Edmund Berke in his speech to the electors of Bristol. Here goes -
'Parliament is not a congress of ambassadors from different and hostile interests; which interests each must maintain, as an agent and advocate, against other agents and advocates; but parliament is a deliberative assembly of one nation, with one interest, that of the whole; where, not local purposes, not local prejudices ought to guide, but the general good, resulting from the general reason of the whole. You choose a member indeed; but when you have chosen him, he is not a member of Bristol, but he is a member of parliament.'
Speech to the Electors of Bristol (1774-11-03); as published in The Works of the Right Hon. Edmund Burke (1834)
What do you say?