In 2014, the Minister for Employment Relations told the House of Commons that workers have a right to rest breaks, and if deductions are made from pay they have to be very clearly outlined, and if they take somebody below the National Minimum Wage, the employer could find themselves in breach of that law.
Nevertheless, ambiguity around workers' rights remains. The TUC knows of many cases where workers have been unjustly penalised for taking a loo break, which is why the TUC is pressing for a change in the law to give people the right to take toilet breaks when they need them. Find out more in the TUC's Give us a (Loo!) break guide.
Currently, employers may be able to deduct pay if there is a clause in your contract stating that you will not be paid for toilet breaks, or if you are away from your workstation. If in doubt, check the terms of your contract to see whether your employer is permitted to do this.