I agree Whitewavemark" that we cannot allow politicians to lie.
Compare the treatment meeted out to Nick Clegg, who had promised in the LibDem manifesto of 2010 not to raise tuition fees, then (in my view wrongly) agreed to allow it when his party were junior partners in a coalition in exchange for the Pupil Premium, compare his treatment with that of Boris Johnson, a man who has been sacked for lying at least twice (by The Times and by John Major).
Nick Clegg was pilloried relentlessly by the right wing media. Boris Johnson not only gets away with habitual lying, but is excused because he's "good old Boris", and ends up as PM, where his constant lying continues unabated and unremarked.