Gordon Brown has been accused of undermining the pro-European campaign by making constant attacks on the European Union.

The chancellor was criticised after inviting leaders of the Britain in Europe campaign to the Treasury.

Guests, such as former foreign secretary Lord Howe, and Lord Brittan, the former European commissioner, told Brown that his negative approach towards Brussels would reduce the prospects of winning the referendum.

One of the delegation said afterwards: "There was a blunt exchange of views. We asked Gordon to make the case for the constitution and to present it as vital to the reforms we want to see in Europe, not a take-it-or-leave-it choice."