The Consumer Financial Protection Bureau is embroiled in tense salary talks, with unionized employees accusing the agency of approving pay raises for senior officials while leaving line employees and middle managers behind.

The CFPB and its chapter of the National Treasury Employees Union have been negotiating salaries, including sessions overseen by federal mediators, for around a year. The union has sought an increase in pay bands, which are the salary ranges for employees of different ranks. The escalating tensions mark the first-ever expiration of a union contract in the CFPB’s history, and add to budget-related concerns at the agency as the US Supreme Court weighs its independent funding.

The CFPB has refused to raise the bands for line employees and lower-level managers, but hiked overall pay levels for the most senior executives, such as associate directors, assistant directors, and others working out of the director’s office, according to about half a dozen union and other internal CFPB emails and documents obtained by Bloomberg Law.