A massive rebellion over House of Lords reform which threatens to tear the Coalition government apart was joined by16 Midland MPs.

And two, Warwickshire MP Nadhim Zahawi (Con, Stratford-on-Avon) and MP Jesse Norman (Con, Hereford and South Herefordshire), were warned to leave the Parliamentary Estate by colleagues, as tempers ran high.

Liberal Democrats are insisting the government press ahead with controversial changes to the upper house – and threatening to block Tory plans to redraw Parliamentary constituency boundaries if they don’t get their way.

Conservatives voting against proposals for an elected upper house included Dan Byles (Con, North Warwickshire and Bedworth), Bill Cash (Con, Stone), Andrew Griffiths (Con, Burton), Chris Kelly (Con, Dudley South), Karen Lumley (Con, Redditch), James Morris (Con, Halesowen), Jesse Norman (Con, Hereford), Mark Pawsey (Con, Rugby), Chris Pincher (Con, Tamworth), Richard Shepherd (Con, Aldridge Brownhills), Chris White (Con, Warwick & Leamington), Robin Walker (Con, Worcester) and Nadhim Zahawi (Con, Stratford-on-Avon).

And they were joined by Labour rebels who also defied their party leaders to vote against the reforms, including Adrian Bailey (Lab, West Bromwich East), Jim Cunningham (Lab, Coventry South) and Geoffrey Robinson (Lab, Coventry North West).

Under plans backed by Lib Dem leader Nick Clegg, the Deputy Prime Minister, the existing House of Lords will be replaced by a smaller chamber of 450 members. Of these, 50 will be appointed and 400 will be elected.

Elections will be held by region, with a total of 33 peers elected to serve a giant West Midlands region taking in Birmingham, Coventry, Wolverhampton and the Black Country as well as Staffordshire, Shorpshire, Warwickshire, Worcestershire and Herefordshire. They would be elected using proportional representation with 11 seats contested every five years.

Although the reform proposals were approved by the Commons, with 462 MPs voting in favour and 124 against, the government was forced to withdraw plans to impose a strict timetable on further debate. It would have lost this vote, because Labour was planning to join forces with Tory rebels, who between them would have defeated the government.

It means that in practice, it may be difficult or impossible to get the changes through the Commons.

But Liberal Democrats are now threatening their own rebellion over government plans to cut the number of MPs in the Commons – threatening a major rift with their Conservative Coalition partners.

Lib Dem deputy leader Simon Hughes said it was up to Mr Cameron to find a way to take Lords reform forward, and warned there would be “consequences” for the Coalition otherwise.

He said: “We are clear you can’t have a deal that is broken by one side without consequences. There would be consequences if they broke it.”

And he added: “The one thing that is obvious that the Tories desperately want is the boundary commission proposals to go through which is an advantage to them.”

Tempers ran so high that rebel Conservative MPs Nadhim Zahawi and Jesse Norman were warned by colleagues to leave the Parliamentary estate, as they enjoyed a drink together after the vote.

Although the warning came from friendly MPs, they were told to leave because others were believed to be ready for a confrontation.

David Cameron was also seen having a disagreement with Mr Norman, after he e-mailed colleagues to argue that voting against the reforms would actually help the Prime Minister. Mr Cameron made it clear that he did not share this view.

The Prime Minister’s spokesman said: “It is not right to characterise it as an angry exchange. He (Mr Cameron) felt his position had been misrepresented (by Mr Norman).”

Explaining his objections to the Bill during the Commons debate, Mr Norman said giving the UK two elected chambers would lead to a repeat of the problems in America, where the two Houses of Congress often disagreed.

He said: “The US offers a useful cautionary tale. The American political system is manifestly struggling: beset by gridlock; vulnerable to powerful special interests, from the gun lobby to the American Association of Retired Persons; and its politicians elected by corporate lobbyists through political action committees, recently liberated by the Supreme Court from any spending constraints under the first amendment.

“The two Houses have repeatedly found it impossible to achieve consensus on important legislation. Pork-barrel has been replaced by stand-off. President Obama’s healthcare Bill is a classic example and it ended up in the Supreme Court.”

Mr Zahawi, also speaking in the debate, said: “The supporters of the Bill would have the country believe that those who are opposed to it are opponents of democracy itself. Today I stand to refute that ugly caricature.

“No one in the House is more committed to British democracy than I. My family immigrated to Britain from an Iraq where democracy was spoken of only behind closed doors, late at night, among trusted friends.

“Compared to the brutal realities of Saddam’s rule, democracy was an abstract dream.

“Yet here in Britain there was a constitutional order which made democracy real, concrete, embedded in the very fabric of our national life.”