The Labour Party do NOT have the right to try to form a government first. That right belongs to the Conservative Party,who have won both the most seats and the largest percentage of the vote.However,they can only form a majority government IF they promise to A) govern in the interests of the country and B) promise to attend to both national AND Liberal Democrat issues regarding the efficacy of the current parliamentary voting system,in which case Mr Clegg,the Lib/Dem leader,has intimated that he might be amenable to reaching some sort of political accord or alliance.
                Mr Clegg ( I don't know him personally,thus I don't call him "Nick",as it would be both rude and presumptuous )has already indicated ,on TV earlier this morning,that he is sticking to his principle of putting himself and his party in the position of supporting,or at least being prepared to be approached by,the party that gains or has gained the most votes, which in this instance is undeniably the Conservative party.
                   Mr Brown will doubtless try to do his utmost to remain as Prime Minister,and is unlikely to resign,however it seems likely that the final arbiter in this instance will be Her Majesty The Queen (God Bless Her),who will, presumably,ask him to state whether or not he is able to form a credible,workable,and legitimate government ; since it appears to be about 99% certain that he will have to answer "No", then that should be the end of that.
                Since we now have a "Hung" ,or as others euphemistically call it, "Balanced" parliament, it is very likely that another election will be called,perhaps within the next two years. Under those circumstances,the Liberal Democrats will,with an eye to future public opinion,be very cautious about just what they are prepared to offer or concede IF any agreement with the Conservatives is in fact reached. We live in interesting times !!