A senior Glasgow SNP councillor has left the party and defected to the Liberal Democrats.

Alex Dingwall, the SNP finance spokesman, has cleared his desk in the party’s office and is expected to be unveiled as a new recruit by leader of the LibDems on the council Dr Christopher Mason today.

The switch is a blow to the SNP’s leader on the council, James Dornan, who has lost an experienced colleague and someone seen as one of his more politically astute councillors.

Mr Dingwall’s defection leaves the SNP with 19 councillors and boosts the LibDem’s to six.

Mr Dingwall was involved when police questioned councillors over allegations of disseminating police information as part of an anti crime crusade involving SNP colleague Billy McAllister.

Mr Dingwall, who represents the Maryhill/ Kelvin ward is believed to have considered quitting following the leadership’s handling of the situation.

There is also understood to have been division within the group over Mr Dingwall’s alternative budget proposals, which proposed even tougher cuts than those of the Labour administration.

In 2008 Mr Dingwall was one of the leadership candidates, defeated by Mr Dornan, following the resignation of John Mason who left to become an MP for Glasgow East.

Mr Dingwall said: “I believe we need a change in how our city is run and a party that sets out a clear, credible alternative to the current Labour administration.

“Regrettably over the last year it has become clear to me that the Glasgow SNP Council Group lacks both the leadership and the authority to set out an alternative vision for our city.

“After 31 years of membership with the SNP the decision to leave has not been an easy one. I am pleased to be joining the Liberal Democrats. I share their commitment to local government and to the principle of keeping local decisions local.

“I will continue to work constructively for my constituents and for the people of Glasgow, but now in a way entirely in keeping with my personal and political beliefs.”