The Commons has voted by big majorities to overturn a series of Lords' amendments over plans to cut the number of MPs and hold a referendum on changing the voting system.
In just a few hours, MPs voted to throw out moves passed during several weeks of debate in the Lords.
These include a proposal to make the result of a referendum on replacing first-past-the-post with the alternative vote (AV) non-binding if turnout was under 40%.
The other votes by MPs, all passed with majorities between 60 and 85, mean the Government’s proposals to cut the number of Parliamentary constituencies from 650 to 600 are still intact.
The scene is now set for a bruising battle of Parliamentary ping-pong between the Commons and the Lords, as the Bill goes back to the Lords on Wednesday.
The Lords must decide whether to reinstate their amendments or to back down.
Lords and Commons divided over voting system plans
In the key vote in the Commons, rejecting the 40% turnout threshold, voting was 317-247, a comfortable Government majority of 70
Opposition MPs are predicting that the Lords will attempt to defy the Commons on a tortuous and at times ill-tempered passage through the Lords.
Government ministers have feared a procedural crisis as Labour peers were blamed for deliberately slowing its progress.
Opposition to the Bill focused on the attempt to redraw the electoral map to reduce the number of MPs, with roughly equal numbers of constituents in each seat.
The Government has blamed a "small number of former Labour MPs" for the hold-up, which saw the Lords sit through the night on one occasion last month.
The Bill needs to be on the statute book before the Lords rises for its half-term recess at the close of Wednesday's business.
This is in order for the Electoral Commission to make preparations for a May 5 referendum on adopting the alternative vote (AV) system for Westminster elections.
