Almost a quarter of MLAs are unelected or have quit their party since the last election.
wenty of the 90 members have been co-opted – meaning they were appointed by their party to replace someone.
Two others are now serving as independents after being elected on a party ticket.
In one case an MLA has been replaced twice, while another quit the Assembly only to return a year later.
An MLA’s pay is £51,000, meaning unelected members now cost £1m a year in salaries.
The high number of co-options has raised concerns around the democratic legitimacy of the current Stormont chamber.
TUV leader Jim Allister said: "It does devalue the democratic credentials of the Assembly if so many MLAs are there not by virtue of anyone voting for them.
"It appears to be a fundamental undermining of the very ethos of a democratically-elected Assembly.”
Currently 70 of the 90 MLAs in the Assembly were elected at the March 2017 election. The other 20 have replaced party members elected four years ago who quit for a variety of reasons.
Some were elected to Parliament in the 2017 or 2019 Westminster elections; others quit to pursue another career. Two passed have away.
Eleven of the 18 five-member constituencies have at least one substitute MLA. Two — Foyle and North Down — have had three changes, meaning over half their members are unelected.
Another, Fermanagh-South Tyrone, will also have three co-options when Arlene Foster leaves the Assembly in the near future. Sean Lynch, a Sinn Fein MLA in the area, stood down last week.
The co-option system was introduced in 2010 after concerns that by-elections could change the political balance in a constituency. It also avoids additional expense — by-elections could cost up to £215,000 a time.
Analysis by this newspaper shows Sinn Fein have made most co-options — replacing 10 of their 27 MLAs.
Four – Barry McElduff, Michelle Gildernew, Chris Hazzard and Elisha McCallion – were elected to Parliament at the 2017 Westminster election. Mr McElduff and Ms McCallion are no longer MPs.
Others resigned for a variety of reasons. Megan Fearon quit as Newry and Armagh MLA, saying she wanted a new challenge, and was replaced by Liz Kimmins. Mairtin O Muilleoir stood down in South Belfast, saying it was time for a new generation of republicans. Deirdre Hargey, the Communities Minister, took his seat.
In West Tyrone, Mr McElduff was replaced by Catherine Kelly, who in turn quit last October over a failure to return money from a Stormont emergency Covid fund, and was replaced by Nicola Brogan.
The DUP have switched four MLAs. These include Carla Lockhart, who was elected to Parliament in 2019 with Diane Dodds co-opted; and Paul Girvan, who was elected as MP in 2017 and replaced by a former MLA, Trevor Clarke.
Simon Hamilton stood down to pursue a career outside politics. He is now chief executive of Belfast Chamber of Commerce. Harry Harvey replaced him.
Gordon Dunne resigned in North Down last month, shortly before his death, after long-term illness, and has been replaced by his son, Stephen.
The SDLP have changed three MLAs, with Claire Hanna and Colum Eastwood elected as MPs in 2019, replaced by Matthew O’Toole and Sinead McLaughlin respectively. John Dallat passed away last year. Cara Hunter took his seat.
Alliance have switched two — with David Ford retiring and Stephen Farry elected to Westminster. They were replaced by John Blair and Andrew Muir respectively. East Belfast MLA Naomi Long had quit Stormont after she was elected as an MEP, but has since returned.
Green MLA Steven Agnew resigned his North Down seat to pursue a career outside politics, with Rachel Woods co-opted.