Investors in outsourced public services firm Interserve are slowly starting to panic, as the group issued a warning that George Osborne’s planned increase to the national minimum wage will make the company’s profits at least 10 per cent lower next year than previously forecasted.

Interserve will need to pay at least 10,000 of its 15,000 cleaners a higher wage as a result - £7.20 an hour by April 2016 and £9 an hour within the next five years. Due to the unexpected nature of the summer Budget announcement, company analysts had not previously anticipated this decline in profits.

Interserve CEO Adrian Ringrose warned that there will also be “knock-on effects”, where more senior workers, such as staff supervisors, will expect their own wage increase to protect their pay differentials from junior employees.

For weekly news updates, subscribe to our email newsletter.

Related: Local councils must find extra £1 billion by 2020 to fund new minimum wage