Pizzas galore!

Mr Howard faced repeated questions from journalists over why his own party was not sticking to the Commission’s recommendations. He insisted that no Tory candidate was doing anything outside the law.

"We are completely within the rules in every respect," he said. "If anybody can offer me an example in which a Conservative candidate is not complying with the rules let me know and we’ll take action to deal with that. We are not responsible for the rules.

"The law is what it is. We have to abide by the law. The Labour Party is doing what the law requires. We have to do what the law requires. I wish the law was different. If there had been a Conservative Government the law would have been different."

The increase comes in the wake of postal voting fraud scandals in Birmingham, where six Labour councillors were found guilty by an election commissioner, and Blackburn, where a Labour activist was sentenced to three years and seven months in jail.

The Electoral Reform Society said yesterday that the huge increase inevitably brought a risk of fraud. "There has been a massive increase since 2001 and this raises both problems of potential fraud and logistical problems for election office staff," a spokesman said.

"We hope that election officials have had a wake-up call from last year and will have put procedures in place to cope with any further increase."

Election officers are privately dismayed by the surge in marginal constituencies. One returning officer said last night: "The parties feel that these people can’t be bothered to walk down to the school or the community centre on election day but they might fill in a postal vote, particularly if canvassers offer to put it in the post."

Another said that a Labour Party expert had claimed: "You need 75,000 votes to win elections in this country and I know where they all are."

However, many prospective candidates were encouraged by the increase. Jim Knight, who is defending Labour’s 153-vote majority in Dorset South, said: "The biggest threat to our majority is turnout, so we are encouraging postal votes wherever we can."

The Times has learnt that the Government has, for the first time in a general election, invited international observers to monitor the last week of the campaign.

The Warsaw-based Office for Democratic Institutions and Human Rights will decide in the next two days whether to accept the invitation. "We don’t investigate and we would not micromanage the police, but postal voting will be looked at if we accept," a spokeswoman said.

Today Lord Razzall, the Liberal Democrats’ election chief, said there was "significant concern" about potential abuse of the system and criticised the Government for not bringing in protections against postal voting fraud earlier. He said: "Political parties always make it easy for people to get the application form for a postal vote. The critical issue is that no political party should be involved in the completion of that ballot form when it arrives."

But Tessa Jowell, the Culture Secretary, said that the problems with postal voting needed to be seen in perspective. She said six of the 17,000 candidates in last year’s council elections had been found guilty of fraud, and told BBC2’s The Daily Politics: "I don’t think you can conclude from what is a relatively small number of very serious cases that the whole system of postal voting is somehow corrupt.

"We have to act where there are weaknesses in the system but that doesn’t undermine the whole system of postal voting. Because credit card fraud takes place doesn’t mean we abandon credit cards."

Times Recommends

• Should Knox’s trial even have reached the courtroom?
• All that glitters is not sold in Wright’s world
• Believe it or not, Big Brother is your friend