The Government has updated its advice on calculating working hours to explain what constitutes a working week.

The Government says job-related training, time spent travelling as part of your job, working lunches, time spent working abroad, paid overtime, any unpaid overtime you’re asked to do, time spent on call at the workplace, any time that is treated as ‘working time’ under a contract and travel between home and work at the start and end of the working day (if you don’t have a fixed place of work) should all count as work.

However, a working week does not include: time spent on call away from the workplace; breaks when no work is done; travelling outside of normal working hours, unpaid overtime that’s volunteered for, such as staying late to finish something off, paid or unpaid holiday and travel to and from work if you have a fixed place of work.

The TUC said the judgement could have implications for many of the 951,000 employees who use home as a base.

But it will have the biggest impact on some 250,000 workers, including 37,000 skilled tradesmen, 13,000 professional drivers who take their vehicles home and 12,000 mobile carers.

The European Court of Justice (ECJ) ruled that employees without a fixed or habitual office – so-called peripatetic workers – should include the time spent travelling between their homes and the premises of their first and last jobs as part of their working hours last year.

The ECJ ruling relates to the working time directive.

It gives workers the right to a minimum 28 days of paid holidays each year, a 20-minute rest break after six hours of work, rest of at least 11 hours in any 24 hours, 24 hours off after seven days of work, and provides for a right to work no more than 48 hours per week over a cycle. It also restricts excessive night work.

However, TUC policy officer Paul Sellers said: “To ensure changes comply, it is important to remember that individual opt-outs from the 48-hour week do not provide complete protection against this judgement, as it also affects the rest break entitlements in the directive.

“In addition, the 48-hour limit opt-out cannot be used by night workers.”