The SNP has been hit by the defection of one of its rising stars in local government to Labour.

South Lanarkshire councillor John McNamee has quit the party, which had initiated disciplinary procedures against him over concerns over his expense claims and were investigating him over alleged “inappropriate behaviour” at a social function.

He says he no longer believes in independence and that he has become disillusioned with the approach he claims the Scottish Government has taken to the west of the country.

Mr McNamee, who represents the Blantyre area, cited the decision to axe the proposed Glasgow Airport Rail Link as a crucial factor in his jumping ship, as well as the impact of the global financial collapse on small nations such as Ireland and Iceland, and the release of the man convicted of the Lockerbie bombing, Abdelbaset Ali Mohmed al Megrahi.

He has also criticised what he describes as the lack of leadership and talent within the SNP at town hall level, describing the two years he has been an elected member as being riddled with in-fighting and that he has been “operating in a political vacuum”.

But the SNP said that Mr McNamee was the subject of “disciplinary procedures” by the South Lanarkshire SNP Group after “concerns were expressed over his expense claims and use of council travel allowances”.

The group was also investigating allegations of “inappropriate behaviour” which Mr McNamee says involved alcohol at a Strathclyde Fire Board event before Christmas, which he attended in an official capacity.

“Councillor McNamee’s conduct would have fallen well short of the standard expected of an elected member,” an SNP spokeswoman said. “Labour must conduct a full inquiry into these concerns before considering councillor McNamee’s application further.”

However, Mr McNamee who sent his official resignation to the SNP’s hierarchy on Friday, accused the SNP of smear tactics and added: “It is totally what I expected.

“I have spoken to the Labour Party nationally and at local level about what is essentially an internal SNP group matter with no other ramifications and they are easy with that.”

Mr McNamee has held talks with the Labour leader of South Lanarkshire Council, Eddie McAvoy, about his move across the council chamber.

He joins only a handful of politicians in recent years to defect and his decision is particularly significant because it comes at a time when an election is expected. There is also speculation in local government circles that the SNP could be hit again by another departure in the west of Scotland in the coming weeks.

Mr McNamee said last night: “There is a real lack of leadership locally for the SNP but the biggest thing for me is that I no longer believe in independence. I’ve lived abroad a bit, in Canada, and travelled in Australia and New Zealand, and come to the belief that economies of small nations really do struggle.

“It’s really hard for me to say after a decade in the SNP, but I believe independence is not an option. For me to continue in the SNP would just be hypocritical.

“All I’ve witnessed since 2007 in local politics is nationalist against nationalist, which is very sad to see. Leadership is lacking, there’s no real strategy and no common purpose, whereas at a local level in South Lanarkshire Labour are delivering.”

When asked if he was aware of others in the SNP sharing the same views, he added: “If they were to be honest with themselves and you ask someone like Derek Mackay (SNP leader of Renfrewshire Council) what he really thinks of the decision to axe the Glasgow Airport Rail Link, I believe you’d get a different answer than what they say publicly.”

Labour’s Michael McCann, depute leader of South Lanarkshire Council, said: “John could no longer be part of an SNP group that was riven with disagreements and had no leadership.

“Like the majority of Scots, John has seen through Alex Salmond and the destructive and divisive nature of his policies.”