LONDON (Reuters) - Citigroup, Bank of America Merrill Lynch (BAML), Credit Suisse and Morgan Stanley all revealed large gender pay gaps in their British operations on Tuesday, the latest banks to report lower average hourly pay for women caused by having fewer female staff in top roles.

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Citigroup had the highest disparity in average pay for women among those banks, disclosing a mean gender pay gap of 44 percent for 2017.

At Morgan Stanley, the gap was 42.8 percent, a spokesman said. Credit Suisse put its gap at 39.2 percent and Bank of America reported a difference of 28.7 percent.

The disclosures indicate how few women have made it to the higher-paid, higher-profile roles in British banking.

The gender pay gap measures the difference between the average hourly salary of men and women, and is different from equal pay considerations, which examine disparity in pay for the same work at the same level of seniority.

The British government has ordered thousands of large UK employers to disclose their gender pay gaps by April 5.

Credit Suisse’s UK chief executive and group chief financial officer David Mathers sent a memo to all UK staff, which Reuters saw.

“For me, these numbers are disappointing, and while they reflect an improvement, there is clearly much work to be done,” Mathers wrote, referring to the fact that the median pay gap had improved to 28.9 percent in 2017 from 31.9 percent in 2016.

All four banks said the main cause of the gap was the higher proportion of men in senior roles.

“Addressing this gap through a more gender-balanced workforce at our own organization, and across the broader financial services industry, will take time,” said Sheri Bronstein, BAML’s global human resources executive, in the bank’s report.

The banks said they had made some progress in recent years, but they have a long way to go before equality is reached.

Citi said its board of directors was 31 percent female, and that women now headed its operations in 26 percent of its countries in Europe, Middle East and Africa, up from 15 percent in 2014.

The pay disparity for bonuses is even higher than for average pay, with Bank of America and Credit Suisse reporting mean gender bonus gaps of 57.9 percent and 70.2 percent respectively.

Morgan Stanley’s mean bonus gap was 72.7 percent, the spokesman said.

The U.S. bank Goldman Sachs disclosed a gender pay gap of 55.5 percent earlier this month.