The Lord Chancellor, Lord Falconer, accepted that there had been difficulties, but said "electoral malpractice is not widespread."
He defended the use of postal voting, which critics say makes fraud easier, as he unveiled planned new laws to be rush
ed through Parliament to tighten up the system .
They will involve putting barcodes and water marks on postal ballots, bringing in a new offence of fraudulently applying for a postal vote - attracting a "significant" jail term - and stopping completed application forms passing through the hands of party activists.
Complaints
Police in West Yorkshire are investigating hundreds of possible fraudulent votes, including 252 in Bradford.
The Lord Chancellor said he was aware of "a number of complaints that are going on" in West Yorkshire.
"We have got to be careful to keep in perspective the number being investigated," he added.
"In some instances two to three hundred votes are being related to one person.
"We do not know what the result of the investigations will be.
"The police have been focusing on this during the election and afterwards and we have to draw a distinction between allegations that go nowhere and those that lead to convictions.
"There are things that need investigation, but my feeling is that there has been no threat to the integrity of the system.
"We will legislate as soon as possible to improve the electoral process."
West Yorkshire Police has confirmed that a number of cases of alleged fraud are being investigated.
anne.alexander@ypn.co.uk
