Constraints on election practices tick all the boxes for the fairest of fights

Voters in seats picked out for special attention by the main political parties as "targets" or "must saves" will already have become familiar with the flap of the letterbox as more unsolicited political material has piled up behind the door for weeks now.

The Political Parties and Elections Act was changed during the most recent parliament to allow for election spending on the "long" campaign, that is, after 55 months since the previous election. The long campaign began on 1 January this year and allowed spending of close to 25,000 per constituency. The "short" campaign begins now.

There are two allowable sorts of campaign spending with specified limits. Parties registered with the Electoral Commission are allowed to spend 30,000 per constituency based on the number of seats contested.

Candidates in the "short" campaign are allowed 7,150 plus 5p per elector in an urban constituencies or 7p per elector in a rural constituency. Most candidates will therefore be allowed somewhere between 10,000 and 12,000 over the next four weeks.

That puts a ceiling of spending for any party contesting every Great Britain mainland seat of 18.96m. The limit for spending in Scotland is 1.77m

In 2005, total Labour spending was 17.94m, including 1.64m in Scotland; Conservatives spent 17.85m including 1.32m in Scotland; Liberal Democrats laid out 4.32m including 435,000 in Scotland; and the SNP spent 193,000 in Scotland.

Profligate though these figures may appear at a time when it can be assumed that the majority of candidates standing will be arguing the looming need to spend less, they are extremely modest in comparison with other major democracies.

Mark Pack of Mandate Communications, and formerly of the Liberal Democrats, says the major difference is that TV advertising is still barred in the UK. Party Political Broadcasts are controlled and represent a small part of party election spending.

"In reality the upper spending limit is not necessarily achieved by the main parties," he says. "What they do, however, is to use the pooled allowance to focus on the constituencies they have identified as their key targets either for gains or those they need to protect. There can be a succession of mailings in those constituencies that the parties believe will help their local candidate but as long as they feature the national leader and all his works it is allowable against the national spending accounts and not the local candidate."

From the outside, that gives force to the assumption parties regard rules as things to be bent. And if that's the approach how well are spending limits policed anyway? Isn't it easy just to overlook an inconvenient receipt or two when post-election accounts are lodged? How could opposing candidates really know what an opponent spent?

In recent times there has only been one prosecution for falsifying general election accounts. Mrs Fiona Jones, elected as Labour MP for Newark in 1997, was convicted at Nottingham Crown Court in 1999 of knowingly making a false declaration of election expenses under the 1983 Representation of the People Act. The conviction was overturned on appeal on the basis the law at the time was difficult to interpret clearly.

Mr Pack says: "The controls work reasonably well. Most often contraventions are rooted in error rather than malice. Scrutiny is the most effective form of policing. The accounts have to be submitted after the election and are pored over by the other candidates, or at least their agents.

"Of course, it is the winning candidate's expenses that are most closely examined and local knowledge of what actually happened shouldn't be underestimated in terms of what ads were taken out, what leaflets went round the doors, or what posters went up. They know what they spent so if an opponent's receipts are for a lot less then that will jump out.

He adds: "In terms of national spending most of the leaflets are sent out through large-scale mailing houses. For them election work is only a small part of their core business and it just wouldn't be worth it for them to take part in some sort of conspiracy to cheat the system by undercharging. Notional spending also has to be included in the accounts."

In recent years, the system of postal votes has been tightened up considerably. They now need a signature and date of birth on the application and on the vote.

Mr Pack says it is harder now to forge votes on a large-enough scale to make a difference to the final result. "Bizarrely, I have been present at many postal vote openings and a number each time were not counted because the applicant put in today's date where they were meant to enter their date of birth," he says. "There is an issue that may need to be addressed because you are not told if your vote is not counted for a reason like that so the error can't be corrected."

Considering how postal vote security has been tightened, significantly there is still no ID check in the UK at the polling booth itself. The offence of personation – casting someone else's vote with or without their knowledge – is difficult to police but the presumption is that it is simply too difficult to do on a large-enough scale to influence the final count.

Candidates should keep in mind other areas of the law, too. While tweets and offensive twits have done for the Labour candidate in Moray, that was another example of self-policing. He was sacked by his party rather than sued by anyone he insulted.

In England, the issue of libel between candidates was addressed in 2005 by Mr Justice Eady in the case of Culnane v Morris.

The same Mr Justice Eady who has been much maligned in the current Simon Singh libel case that has raised issues of freedom of academic speech delivered a very liberal interpretation of what would be acceptable for candidates to say about each other in the hurly burly of a campaign.

But just as in candidates' allowable spending, there will be limits.