The DUP has written to the Parliamentary Standards Commissioner about Sinn Féin MPs not including wages received from the party on their register of interests.
Sinn Féin MPs do not receive a salary from Westminster as they do not take their seats, but the party has said it pays them a wage from its own resources.
However, none of the seven MPs include details of their party wages in their Westminster register of financial interests.
Read more: Renewed optimism but no breakthrough in Stormont talks on Brexit NI Protocol
DUP South Down MLA Diane Forsythe said she has written to the Parliamentary Standards Commissioner and the Electoral Commission to seek an explanation.
It follows recent scrutiny of the financial interests of MPs.
Sinn Féin MP John Finucane was 20th in a list of MPs earning the most from jobs outside of Parliament, according to an analysis by Sky News and Tortoise.
The North Belfast MP works up to 20 hours a week for his law firm, according to his register of interests.
He is the only Sinn Féin MP who declares any income under the category "employment and earnings" on the register.
Sinn Féin said its MPs are "fully compliant" with the register of interests at Westminster and "all relevant interests are declared in line with the rules".
But the DUP's Ms Forsythe said: "Sinn Féin has declared that these MPs are 'employees' of the party and are paid as such, yet this does not seem to be declared in their register of interests.
"Is this another example where Sinn Féin believes rules are only for others to follow?"
"With millions flowing into Sinn Fein bank accounts, there is no cost-of-living crisis in Connolly House but Sinn Féin elected representatives must properly declare the financial interests."
Sinn Féin's wage bill in Northern Ireland is more than every other Stormont party combined.
Wage and salaries expenditure for the party's northern operation was £799,334 in 2021 accounts filed with the Electoral Commission.
The documents said the equivalent of 15 full-time staff were on the payroll. The party last year said this included their seven MPs.
It would suggest the bill averages at more than £53,000 per full-time role. However, Sinn Féin insisted the bill also includes another three full-time staff paid through a Stormont funding allowance. If included, this would bring the average to around £44,400.
In the past Sinn Féin had long maintained all its MLAs and MPs accepted an "average industrial wage" with the rest donated to the party and constituency matters.
But in 2018, the party said a review of its wage structures two years previous led to a "recommended party wage" which is "entirely voluntary".
In a statement, Sinn Féin called on the DUP to end its block on Stormont power-sharing in protest against Brexit's Northern Ireland Protocol.
A party spokesperson said: "The focus of Diane Forsythe and her DUP colleagues should be on doing the job they were elected to do.
"They should get back round the Executive table to work with the other parties as patients continue to suffer and our health workers are crying out for support and political leadership, as staff and services are being overwhelmed and actually do something for the people struggling with the cost of living crisis.
"Sinn Féin regularly engages with the registrar's office and Sinn Féin MPs are fully compliant with the register of interests at Westminster and all relevant interests are declared in line with the rules."
The Parliamentary Standards Commissioner was approached for comment.
READ NEXT:
- TUV Assembly election candidate becomes DUP councillor
- DUP slammed for 'cherry-picking' health report to attack NI Protocol
- NI secretary Chris Heaton-Harris apologises for 'deeply unpleasant' posts after Twitter account hacked
- 60% of MLA staff recruited since NI Assembly election are party members
For all the latest news, visit the Belfast Live homepage here. To sign up to our FREE newsletters, see here.
