The 59-year- old, a party heavyweight, said it was a 'noble endeavour' to stop the 'slow strangulation of fundamental British freedoms'.

But the extraordinary gamble with his career and the wider fortunes of the Conservative party astonished and infuriated his colleagues.

There is also the risk his decision could backfire if the Labour party refuses to field a candidate.

The Liberal Democrats have already said they will not fight the by-election, which could leave Mr Davis in the embarrassing position of debating only with candidates from fringe parties such as UKIP and publicity-seeking independents.