The pay gap in the Metropolitan police between white officers and their black and Asian counterparts has widened in the past year despite promises to close the divide, new figures have shown.

A Met study of average wages found that black and Asian police officers working in London were paid £1.80 an hour less than their white colleagues last year, compared with £1.52 in 2017. All 37 senior officers on salaries of £100,000-plus were white, it found, while ethnic minority officers received fewer and smaller bonuses than their colleagues.

The report, which looked at the pay of 37,257 Met employees, of whom 6,349 are Black, Asian and minority ethnic (BAME), found the gap was even worse when all staff – not just police officers – were taken into account. On average, it said, BAME staff receive £2.05 less per hour than the average white member of staff, a mean pay gap of 9.67%.

These findings, the second ethnic police pay audit by the Met, will increase the pressure on police commissioner Cressida Dick to take action. Last year the mayor of London, Sadiq Khan, pledged change after a pioneering pay audit found that the city’s BAME public employees were paid anything up to 37% less on average than their white counterparts. It revealed that the pay gap was “particularly stark” at the Met, the Greater London Authority and the two development corporations.

Met director of human resources Clare Davies, who compiled the report, said: “It is important to stress that police officer and police staff pay is determined in accordance with roles. BAME and white officers and staff who undertake the same role have the same length of service and work the same hours, therefore receive the same pay. Nevertheless, when considering average pay across the workforce, differences are apparent.”

One of these differences is in bonus pay. The Met pays a number of bonus payments of up to £500 for those who have excelled in the performance of their duty, or lump sum payments for retention initiatives. The proportion of white officers receiving a bonus payment is 1.23% (371 officers) compared with 0.83% (53 officers) BAME officers. On average the bonus paid to a BAME officer was almost £20 less than that paid to a white officer.

On Saturday the force issued a statement saying: “The report makes it clear that police officer and police staff pay is determined by role with no reference to ethnicity.

“BAME employees who undertake the same role, have the same length or and work the same hours, receive the same pay as white employees.” But the statement noted: “Perversely, recent improvements in recruiting more BAME officers and staff also works to increase the gap: an increasing proportion sit in the lower pay spines lowering the average; this will improve as newer recruits progress their careers and move their way to the top pay points.”

It added: “Since reporting in 2017, the Met has seen a very slight reduction in the overall median pay gap from 16.7% in 2017 to 16.15% in 2018. Much of the difference for both police officers and police staff results from historical allowances, which have now been removed.

“As more BAME officers and staff have shorter length of service on average, they are less likely to receive these historical allowances. Due to their shorter length of service they are also less likely to be at the top of pay scales or represented in higher paid roles.”

• The headline on this article was amended on 21 January 2019. An earlier version referred only to “black police” being paid less than white officers.