Almost two million people across the country have voted by post already, including tens of thousands in marginal seats.

The figures, from a Telegraph survey of 21 seats, would suggest almost a quarter of postal voters have already cast their votes.

Returning officers in Dumfries and Galloway, Northampton South, Milton Keynes North East and Hammersmith and Fulham had received over 3,500 postal ballots by April 28 - well up on 2001 totals.