The suspension of a leading Labour councillor has thrown the balance of power at Monmouthshire County Council into question.

Labour often has to rely on the casting vote of the chairman to win crunch votes on Monmouthshire County Council where it leads a minority administration in coalition with the only Green Party councillor which is dependent support from an aligned independent.

The party’s fragile grip on power at County Hall in Usk was underlined at the annual general meeting, in May, when Labour’s Mary Ann Brocklesby only saw off a Conservative challenge to her leadership thanks to an independent councillor’s abstention.

Now Labour’s ability to push its agenda through the council has been further harmed by the suspension of Councillor Tony Easson who represents the Dewstow ward in Caldicot.

Among key business the council is expected to have to decide in the coming weeks is the replacement local development plan, which has to be passed by a majority of the full council, and is crucial to Labour’s plan to massively increase the number of affordable houses built in Monmouthshire.

No reason has been given for the suspension of Cllr Easson, who is in his 80s, but he has said he thinks “it can only” be related to a dispute involving him, and other members, of Caldicot Town Council related to complaints from councillors over its clerk.

The retired steelworker and longstanding member of the Labour Party who has been a county councillor since 2012, said he had been informed he had been suspended from the Labour group at County Hall due to a complaint.

He said: “I had a message after the (August) bank holiday somebody had complained they’ve got to investigate and until such time as the investigation has been completed I can no longer be a member of the Labour group.”

He added: “It’s obviously related to that problem in the town council.

“As far as I’m concerned I don’t know exactly what it’s about but it obviously related to that problem on Caldicot Town Council.”

Labour leader Mary Ann Brocklesby confirmed Cllr Easson had been suspended. She said: “He has been suspended by the Labour Party. I don’t know the full reason for the suspension and you would have to contact the Welsh Labour Party press office.”

Asked how the decision would impact Labour’s management of the council the leader said Cllr Easson would be expected to follow the Labour whip.

Cllr Easson, who said he is still expected to pay a financial levy to the Labour Party, said he would vote “with my conscience”.

“I’ve been told I should still follow the whip but I’ve had the whip taken of me so I can’t follow the whip.”

Monmouthshire County Council’s website has shown Cllr Easson listed as a “not specified” independent. He said he intends asking the council to show him as an “independent socialist”.

Following Cllr Easson’s suspension Labour has 20 members on the council, the Conseratives have 19 and there are two councillors in the Green Independent group that includes the Green Party’s Ian Chandler who has formed a coalition with Labour, and four councillors in the Independent Group. Cllr Easson is the only one of 46 councillors outside of any group.

Welsh Labour has been contacted for comment.