Liberals argue Labor's electoral reform package should stand or fall as a whole in any court challenge

An attempt by the Liberals to insert a potential legal time bomb into the electoral reform legislation and a Labor proposal that would give the ACTU a generous donation cap were main reasons an expected bipartisan deal on the bill imploded at the last moment this week.

Under a "purpose of bill" provision pressed by the Liberals, if there were a successful High Court challenge to part of the legislation, the whole