The papers had been printed in London and were being taken to two constituencies – Hastings and Rye, and Eastbourne – before voting in the general election on 7 May.

The Metropolitan police, which are investigating the theft of the vehicle from Dagenham in east London, has informed Hastings and Eastbourne councils.

Officers found nothing to suggest the white Mercedes van had been targeted for its contents or that the theft was an attempt at electoral fraud. They told the local authorities they believed it was a coincidence the stolen van contained ballot papers. The theft took place overnight.

The vehicle contained 72,300 voting slips for Hastings and Rye, and 130,000 for Eastbourne. A Hastings council spokesman said: “We have been in touch with the Electoral Commission and, following their guidance, we have put a process in place which will ensure that these ballot papers are not used for fraudulent purposes and cannot be included in the count.”

A spokesman for Eastbourne council said replacement ballot papers were being printed on different coloured paper to the original batch, so any stolen papers placed in ballot boxes could be easily detected and removed.

The Electoral Commission said it was liaising with council officials.