No-one can possibly overestimate the scale of the disaster which hit Gordon Brown and the Labour Party in the Glasgow East constituency in the early hours of this morning.

Here was a seat which has been a fortress for Labour in Scotland where Labour did not so much count their votes as weigh them. And yet, they saw their 13,507 majority overturned by a triumphant Scottish National Party (SNP).

The shock of this result casts another huge pall of gloom over the Prime Minister as he goes on his annual holiday. It raises massive questions about his continued leadership of the Labour Party.

Backbench MPs will have to face the fact that the Glasgow East result, after a similar by-election disaster in Crewe and Nantwich in May, makes Mr Brown look like very damaged goods as their leader. They must now ask themselves if they can possibly win a general election under Mr Brown and the Prime Minister’s Cabinet colleagues will no doubt be asking the same question.

The major concerns for many households in one of the most deprived areas of Britain were the rising cost of fuel and food, the ongoing rate of street crime and the whole issue of law and order generally. But voters were obviously angry at the non-appearance of Mr Brown in the constituency during the by-election. Labour also suffered from the refusal of their first choice candidate to accept the nomination and that Margaret Curran was a 4th choice.

Mrs Curran fought a focused and largely sure-footed campaign, and still Labour lost with thousands of previously rock-solid, loyal voters turning their back on the party that their families have supported for generations and administering the political equivalent of a mugging.

Alex Salmond, the SNP leader and Scottish First Minister, had promised a political earthquake in this by-election and he delivered, although some might say this was a tsunami rather than a mere earthquake. They will conclude that in Scotland there are very few Labour seats safe from their incursions. By taking Labour’s third safest seat in Scotland, they have proved that last year’s win in the Scottish Parliament elections was no one-day wonder and that they are now Scotland’s leading party while Labour in Scotland goes into freefall.

This may have been a protest vote by people in Glasgow East fed up with rises in the cost of living. But it also showed that Labour’s core support in Scotland is also now so thoroughly fed up with Labour that they think nothing of voting for the party’s main political enemy in order to teach it a lesson.

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