You are an MP, staring glumly at the latest election results and wondering how to restore public respect. What is your first idea?

Incredibly, it is to dream up a palatial new debating chamber, vaguely costed at some half a billion, in the heart of the Westminster village. It will be lavishly furnished with sports facilities and guarded with a “security pavilion” inside an armed encampment. The project will be temporary, just for five or six years, since at the same time you will be spending another £4-6bn of taxpayers’ money refurbishing the even more splendid Palace of Westminster, a hundred yards down the road.

This week’s Commons decision on how to decant itself into temporary accommodation beggars belief. It suggests a parliament cut off from public opinion, contemptuous of the rebellious distaste for politicians suggested by recent election results.

No one doubts that the Houses of Parliament must be restored, though the need to decant entirely must be debatable. The Commons moved into the Lords during the war (and the Lords to Church House). Most MPs attend the actual chamber only three days a week, and it is mostly deserted most of the time. Committees meet elsewhere.

Even if MPs do feel the need to move, several sites close by have been suggested as temporary venues. They include the atrium of Portcullis House next door – with a proposal put forward by its architect, Sir Michael Hopkins – as well as temporary structures in the courtyards of the Treasury and Foreign Office, Church House and the Emmanuel centre in Marsham Street. The developer Sir John Ritblat has offered a dramatic prefab in Horse Guards Parade, designed by Norman Foster and built at no cost to the public beyond an annual rent, that could be later rebuilt elsewhere. It would save hundreds of millions of pounds.

Not only has no evaluation of these options been made public, no mention has yet been made of cost. The Commons leader, Andrea Leadsom, instead played the Notre Dame card, that any objection risked a catastrophic fire. But this is like the French government demolishing buildings on the Île de la Cité to build a facsimile Notre Dame next door.

The most imaginative solution would be for the Commons to decamp three days a week to suitable buildings in central Birmingham or Manchester, while Westminster is restored. It would shake up parliament, help to reunite a divided nation, and refresh the image of British politics. Contact with government offices could be digital. Commons work that has nothing to do with the chamber could continue in London. Any inconvenience would be the price MPs pay for decades of poor custodianship of the Palace of Westminster.

Oddest of all is the process of this decision. It is clear that Westminster’s inhabitants have lost all sense of guidance or leadership. They appear to be in the hands of a cabal of MPs headed by Leadsom, and the Speaker, John Bercow. As at all such points in these mega-projects, the decision tends to be hijacked by consultants, with a vested interest in their original plan, egged on to extravagance by their Whitehall comrades-in-arms, the security lobby.

The public is being asked to build a new Commons, apparently to be used afterwards for “a learning project”. We are tempted to ask, learning what? Why a facsimile House of Commons should linger on inside a militarised enclave is unclear.

It will eradicate all but the street facade of Richmond House, designed by Sir William Whitfield, who died last month. This was erected in the 1980s with massive reinforcement to resist IRA bombs, crafted to sit harmoniously alongside its neighbour, Norman Shaw’s New Scotland Yard. It is Whitfield’s finest building and to lose it for any temporary use is bizarre. Imagine what MPs would say if a hospital, university or town hall treated public money like this.

This project is a major state commission. Yet there has been no revelation of any competition, which is surely irregular. The design is rumoured to have been repeatedly changed, as MPs fastidiously demand identical facilities to those at Westminster – green benches, voting lobbies and all. They regard it as anathema to grasp this rare opportunity to experiment with new voting systems or a less confrontational layout, such as a semi-circular chamber. The old palace was designed in 1836 by Sir Charles Barry to look like a cosy West End club. So it apparently must be, for ever.

Trapped in pre-austerity mode, MPs are here celebrating the 10th anniversary of their expenses scandal by laughing in the face of their public image. The river wall of the Palace of Westminster was given steps leading down into the water, so that MPs could escape if Parliament Square were ever besieged by a riotous mob. I assume the steps are being repaired.

• Simon Jenkins is a Guardian columnist