Michael Howard says that Tony Blair should be "deeply ashamed" that he rejected recommendations from the Electoral Commission to reform postal voting.
He quoted remarks by election commissioner Richard Mawrey QC that the postal voting system is "wide open to fraud" after results in two wards in local elections in Birmingham were declared invalid due to fraud.
Labour's culture secretary Tessa Jowell says that a small number of very serious cases doesn't mean the whole system is corrupt.
The Labour Party has been keen on postal voting in order to encourage more people to vote. In the 2001 election, only 59% of eligible voters went to the polls, the lowest turnout since 1918.
There were 1.3m postal ballots cast in the 2001 general election, and some estimates suggest that as many as 6 million people will request postal ballots this time.
The law on postal ballots was changed in February 2001 to allow any local elector to vote by postal ballot after a written application.
All the political parties are keen to encourage more postal votes among their supporters.
So they have been encouraging potential postal voters to send their requests for a postal ballot direct to their offices.
This is not strictly illegal, but it is against the spirit of the election commission code of conduct that was agreed between the parties.
It says that "the local election registration officer's address should be the preferred address given for the return of application forms".
And it adds that if postal ballots are sent to political parties "forms should be despatched unaltered to the relevant electoral registration officer's address within two working days of receipt".
The electoral fraud uncovered in Birmingham involved not only help in completing applications for postal ballots, but falsely completing the ballot papers along with false witness statements.
These are illegal acts under Representation of the People Act that could lead to prosecution.
But no one knows how widespread they might be.
The high court judge in Birmingham has said that the postal voting system is "hopelessly insecure" and that "short of writing 'Steal Me' on the envelopes, it is hard to see what more could be done to ensure their coming into the wrong hands".
All three political parties believe that increasing turnout among their own supporters is the key to electoral success this time.
Therefore they are all encouraging voters to send requests for postal ballots to their own supporters despite the code of conduct.
As Parliament is not sitting, wider reform of the postal ballot system will have to wait until after the election - where the balance between encouraging greater turnout and opening the system to potential fraud will have to be re-examined.