Proportional representation is not worse than Labour

There is nothing inherently libertarian about first past the post and so there is no particular reason why a party of the right would support it. Fptp doesn't reduce the size of the government any more than pr does (in fact there are good arguments to show the reverse) and so there is no reason to resist pr. Pr would not be worse than government under the centre-left (Labour) party... to be ruled by Labour is not preferable to pr.