Sinn Fein assembly member Gerry McHugh has resigned from the party over the direction he feels it has taken.
Mr McHugh will still sit in the assembly as an independent
The Fermanagh/South Tyrone MLA told a local newspaper he had become disillusioned with "the undemocratic nature of the party".
Mr McHugh will still sit in the Northern Ireland Assembly as an independent.
Sinn Fein has said it is disappointed with the decision and was not aware of any problems.
'Well aware of policies'
In a statement to the Irish News, Mr McHugh said Sinn Fein had become "overly controlling of members".
"I have become increasingly disillusioned with the totally undemocratic nature of the party and the totally top-down dictation within it," he said.
"I feel the direction Sinn Fein is taking is more about appeasement of the British government and administrating British rule in Ireland rather than working towards the end of British occupation."
Sinn Fein assembly group leader John O'Dowd questioned why Mr McHugh failed to raise issues of concern within the party.
"Obviously it disappointing that Gerry did not raise any of the issues he is claiming led to his resignation within the assembly team prior to going public with his decision," he said.
"Gerry has been a member of the party for a number of years and is well aware of our policies in relation to issues such as policing.
"Our special ard fheis was held months before he allowed his name to go forward as a Sinn Fein candidate in the assembly elections.
"It was on this basis that Gerry McHugh was elected."