The chief executive of Glasgow City Council has broken his silence on the controversial departure of Steven Purcell, insisting that city improvements in recent years were not due only to the former leader.

In an e-mail to council staff, George Black said that reports of Mr Purcell’s problems with cocaine and alcohol and allegations over his political dealings had attempted to devalue the authority’s achievements.

But he added: “Nothing could be further from the truth. In the last five years the council, and the city, has been transformed, not because of the person who was in charge but because of the hard work and dedication of you and your colleagues.”

Mr Black also said that “strong political leadership” helped in dealing with the financial circumstances the public sector has found itself in.

But opposition leader at the council, the SNP’s James Dornan, described the letter as inappropriate, claiming it appears supportive of the council’s ruling Labour Party.

He added that the letter did not reassure staff that the council was investigating the recent allegations.

Mr Dornan added: “Mr Black should not be making statements which seem supportive of political parties.”

A council spokesman added: “Mr Black believes, as does Audit Scotland, that strong leadership is vital in running a council.”

Meanwhile, it was confirmed a special council meeting, called for by the SNP group, will be held this month to discuss the circumstances of Mr Purcell’s resignation on March 2 due to stress and exhaustion.