Louise Mensch and Nick Clegg boost the prospects for a Labour government

This has been a monumentally bad week for the Coalition government. Indeed, it could turn out to be the week we look back on as the turning point in making the election of a Labour government in 2015 probable rather than merely possible.

The shock resignation of high-profile Tory MP Louise Mensch a little over two years after being elected is potentially a gift to Labour. Her seat of Corby and East Northamptonshire is marginal and in the current political climate looks a near certainty for a Labour win. British politics since the war has been hugely influenced by the momentum that parties have been able to build on by-election victories and there is no reason to suspect the same will not happen again following this contest.

With the government having become incredibly accident-prone since the Budget, it looks as if Labour needs to do little more than play safe to snatch this seat. Of course, a major blunder on their part in candidate selection or on the national stage could change this with disastrous consequences for Ed Miliband's leadership but I don't think that very likely.

One slightly intruiging possiblity is the suggestion that the Tories could put London mayor Boris Johnson in as their candidate. Now, strange things  happen in polictics but I can't see this being one of them. Why would David Cameron offer Boris a way into Parliament when there are some in the Conservative Party already talking about him as a potential successor as leader? There would also be the rather big problem of how to fill the vacancy for London mayor. I am not sure of the rules on this but if it were to result in a London-wide by-election this could be another, bigger, gift to Labour. It was probably only Boris's personal charisma that held it for the Tories earlier this year so take that away and they would be in trouble in the capital.

Alongside this electoral test the fracturing of the Coalition over constitutional reform has reached a crisis point.

The Prime Minister's unexpected decision to ditch the plans for an elected House of Lords has, in turn, jeopardised the proposed reduction in the number of MPs and the equalisation of constituency sizes.

When Parliament rose for its summer recess it did look as if the government was united in its determination to give the plans for reform of the House of Lords one last major push in the autumn. I always thought that if that failed to move the legislation on significantly then the Tories would quielty pull away from supporting it but did not expect this premature wholesale abandonment. After all, it has been in the Tory manifesto for ten years and was a key feature of the coalition agreement. It will be very interetsing to see what the next Tory manifesto has to say about Lords' reform after this. However, that is in the future.

The immediate consequence was that Liberal Democrat leader Nick Clegg announced a tit-for-tat withdrawal of support for the reduction in MPs and the boundary changes. This is a serious rift in the coalition and significantly reduces the chances of it surviving the full five years of this Parliament. In the context of the next General Election it is a major boost to Labour as it stood to lose up to 20 seats as a result of the boundary changes because many of the urban seats it holds have small electorates so the equalistaion of voter numbers would have hit Labour hard.

So, without having to lift a finger Ed Miliband has moved quite alot closer to No 10. I suggest the financial services sector starts working very hard to get to know those who might in less than three years time hold its fate in their hands.