I think OP means the prime minister has to be voted in by his own party's members of parliament - and OP trusts the integrity and foresight of 300 MPs more than

I think OP means the prime minister has to be voted in by his own party's members of parliament - and OP trusts the integrity and foresight of 300 MPs more than that of the unwashed general electorate. (He might have had a point 50 or 100 years ago when the majority of MPs took pride in integrity and public service and weren't mostly full-time party hacks and climbers of the greasy pole...)