Nobody wants a criminal record, but sometimes prosecution is the only course of action. If the worst does happen, you need to ensure that you minimise the damage to the environment as soon as possible, thereby minimising the damage to your reputation and the likely costs of fighting a criminal prosecution.
Since 2014, courts have been using a sliding scale of penalties based on two main factors – how much the offender was a fault and how much damage was caused. Additional factors such as the size of the company, how quickly action was taken to minimise or repair any damage, how readily the offender admitted liability and cooperated with authorities, the previous ‘character’ of the offender and the steps taken to prevent recurrance of the offence can affect the final level of penalty, but the minimum level is determined on the two main factors.
In essence, a small company who have accidentally (and for the first time) caused slight damage that they immediately cleared up and reported may be fined the minimum amount of between £500 and £2,500. A multi national company, committing their third breach in as many years, causing actual damage – perhaps to a watercourse where fish died – may expect a fine in the range of £1,000,000 to £3,000,000, or possibly more if the courts determine that there are aggravating factors. In a 2015 Court of appeal ruling (R v Thames Water Utilities Ltd  EWCA Crim 960) the Court stated that where warranted, very large fines – even up to the complete pre-tax profit of a company – might now be imposed.
We can provide specialist advice to your legal team if they are not environment specialists.