Brent East has thrown into sharp focus the problems facing the three main parties.

The real question is whether the by-election result is a blip or a turning point.

For Labour the result shows how much work the party has to do at both the local and national level.

On the doorstep in Brent East there was utter contempt for the Labour-run council and despair at the high level of violent crime in what was once a quiet suburb.

The constituency is now a place of social extremes due partly to property developers and gentrification.

The most ethnically diverse constituency in London has some of the poorest residents living next to areas where houses routinely cost £500,000.

Many voters are low-paid public sector workers who live at the sharp end of "reform" and two-tier workforces.

Among Labour's core vote is a feeling that they have been left behind by the party that claims to represent them.

It offered them a white, middle class, middle-aged, professional politician - who it was later revealed lived in the Surrey stockbroker belt - as the person to represent them in Westminster.

Added to this was the Iraq factor which, though down the list of priorities, has added to the sense of disconnection.

The high vote for independent protest candidates - and the sheer number of them - shows deep dissatisfaction with the government's direction in a Labour heartland.

Most painful for Labour's leadership will be the fact that they had to rely on London mayor Ken Livingstone - Brent East's former MP - to drum up support.

For the Conservatives, the result is likely to trigger all the questions that party leader Iain Duncan Smith had hoped the local election results of earlier this year had ended.

Claims that its core vote held up do not explain how it ended up in third place.

The party came second at the last election and should have been able to capitalise on the government's current discomfort.

Had the Conservatives not selected a local candidate the result could have been even worse.

And its inability to mobilise activists was thrown into sharp focus; the lack of canvassers and tellers at the polling booths limited its ability to get its message across.

Party chairman Theresa May had to admit that the constituency was "not natural Conservative territory".

Two years ahead of its 1997 election victory, New Labour was romping ahead in the polls and piling on the pressure. Brent East shows the Tories have yet to widen appeal beyond its natural support base.

Charles Kennedy's challenge has in effect only just begun.

Grumbles about the Liberal Democrat leader's commitment earlier this year look pointless when set against the fact that he became a semi-permanent fixture in Brent with six visits before polling day.

His problem is ensuring the party retains the seat at the next general election.

Brent East's new MP, Sarah Teather, started with the advantage of already having been selected for the general election and had been campaigning well in advance of Paul Daisley's death.

And the extraordinary campaign machine that the Liberal Democrats have created was also a key factor.

Teather told ePolitix.com that the party could deliver a leaflet to every home in the constituency in a day. Each day around 300 activists from across the country poured in to help and she claimed that on the final weekend, the number reached 1000.

In an era when party activism is unfashionable, being able to call on this level of manpower is an achievement in itself.

The pro-public services message, together with the Liberal Democrat's anti-war stance, provided a home for disgruntled Labour voters. Will they stay?

Brent East throws up questions that each of the parties must answer.

Is this a temporary blip or another signal that a shift in public sentiment is underway? Is there a genuine move away from the two party system which has largely dominated the political landscape through the last two centuries?

Have the Liberal Democrats made the breakthrough needed to mount a serious challenge to the Conservatives at the next election?

The Conservatives need to win back seats they once held in the 1980s such as Basildon, Enfield Southgate and Edinburgh Pentlands. On present form, that is a long way away.

For Labour, "trust" is now the key issue above the euro, Iraq and reforming public services.

The party pointed to new schools, multi-million pound building projects and even the new Wembley stadium to show how much cash is going into Brent East - all to no effect.

The government must now re-examine the way it does business with the electorate. And it has just two years to do it.