I fail to see how this is consistent with any concept of due process as well as innocent until proven guilty in a court.
Their main role is to issue parking tickets but under legislation brought in last year they will also have powers to give on-the-spot fines for anti-social behavior.
On the spot fines in Britain mean you get given a penalty notice (for minor crimes only, like speeding, parking etc). You then have a choice, to pay the penalty fine by sending it off with payment or taking it to the court office etc, which means you admit guilt. The alternative is you deny the offence, or claim extenuating circumstances, in which case you go to court and argue your innocence. The penalty will be larger if you go to court and are found guilty.
So the principle of innocent until proven guilty still exists, because if you refuse to accept guilt and pay the fine, which you have every right to do, they have to prosecute you in court.