The official elections watchdog has issued a warning against any attempt at ballot-rigging through the postal voting system in the forthcoming General Election.
The Electoral Commission set out a new code of conduct for candidates and campaigners involved in the handling of postal votes in a bid to restore confidence in the system.
The postal voting system was denounced last week as "an open invitation to fraud" by a High Court judge during a hearing in Birmingham into alleged ballot-rigging.
Although the commission stressed that its new guidelines were not a response to the Birmingham case, it acknowledged that action was needed to "minimise the risk or perception of fraud".
The commission's chief executive, Peter Wardle, said the guidelines were part of a wider package of measures aimed at "improving the integrity of the voting process".
He said: "Our code aims to strengthen the postal voting system so that people can be confident of the same standards of behaviour they expect at polling stations".
The new code - which applies throughout Great Britain but not Northern Ireland - is supported by all the main political parties.
Although it is only voluntary, the commission made clear that it would call for legislation if self-regulation by the parties failed.
It is also working with the police and prosecuting authorities to provide practical guidance for local police forces on how they should deal with any allegations of voting fraud which arise.
With postal voting available on demand since 2001, the commission is predicting that up to 15 per cent of the electorate will choose to cast their vote by post in the General Election expected on May 5.
The code advises candidates and campaigners not to handle postal ballot papers or to help voters complete them and to encourage voters to post or deliver their ballot papers themselves.
If they are asked to take a completed ballot paper, they should ensure that the voter has sealed it first and then immediately post it or deliver it to the returning officer.
They should also ensure that voters complete ballot papers in secret and then seal them personally.