More than 60% of constituency office staff recruited by MLAs since last year's Stormont election are party members, according to Assembly documents.
Some 70 of the 106 forms submitted by MLAs since May to register each new employee on their payroll declared a connection.
Sinn Fein MLAs recruited the most so-called "associated persons" during the period, with all 24 of its payroll forms for new staff disclosing their party membership.
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The Alliance Party was second with 22 forms declaring associated persons out of 35 submissions, followed by the DUP with 15 out of 34.
Five of the eight forms submitted by UUP MLAs recorded associated persons, while all four for the SDLP declared the link.
The details were revealed in a Freedom of Information response from the Stormont Assembly to Belfast Live.
Under Stormont expenses rules, "associated persons" include party members, former elected representatives, and relatives or former employees of other MLAs.
While MLAs are required to declare the employment of associated persons and explain the connection, this information is not routinely made public.
By contrast, the employment of family members is publicly disclosed on MLAs' register of interests. Around one in seven MLAs employ family members in their constituency offices.
A total of 106 submissions were made by around 50 MLAs between May 13 and November 15 last year, according to the FOI response.
Of the 70 New Support Staff Payroll Forms which declared associated persons, 64 were recorded as party members.
The other six - three for DUP, two for Alliance and one SDLP - were considered associated persons for other reasons, such as being former employees of other MLAs.
Five of the payroll forms said the new staff member is also a party councillor.
Assembly records show MLAs claimed almost £8million in expenses for staff costs between April 2021 and March 2022, the most recent period for which figures are available.
In 2020, MLAs increased staff wages as they abandoned having office expenses rules set by an independent panel.
The powers were given to the Assembly Commission, a body which runs Stormont and is made up of representatives of the five main parties.
Constituency office staff can now earn up to £37,180 a year, with total annual employee wages per MLA capped at £82,400.
Secretary of State Chris Heaton-Harris reduced MLA salaries by 27.5% from January 1 to £37,337 due to Stormont's collapse.
The devolved institutions have not been fully functioning since last February when the DUP withdrew from power-sharing in protest against Brexit's Northern Ireland Protocol.
If a new Executive is not formed by January 19, the UK government assumes a legal responsibility to call a fresh Assembly election by April 13.
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