The process for deciding on complaints of misbehaviour by local councillors is "fundamentally flawed", according to the Committee on Standards in Public Life.

A report published by the committee on Wednesday took ministers to task for failing to implement previous recommendations on how claims of misconduct in local government should be investigated.

Chairman Sir Alistair Graham said that the legislative framework for ethical standards in town halls would have to be rewritten.

Current arrangements mean the Standards Board for England (SBE) has to investigate every complaint, even though many are "vexatious" and "politically motivated", said the chairman.

The report concluded that the standards board had "struggled to perform a strategic role within the existing legislative framework".

"It has been preoccupied with trying to handle all complaints made against councillors in England irrespective of the seriousness of the complaint made," said the committee.

"This is a role imposed on the board by legislation but, in the committee's view, this is not sustainable and will, if unchecked, erode confidence in the ethical framework itself."

Sir Alistair added that local standards committees should have more responsibility for dealing with minor complains, with only the most serious cases referred up to the SBE.

But in return for their new role, the local watchdog committees should be strengthened by the inclusion of more independent experts.

Such changes could save money, Sir Alistair added, as the SBE needed a "large bureaucracy" to sift through all the complaints referred to it.

In addition, the large backlog of minor complaints meant that many councillors faced delays that left allegations hanging over them.

And the code of conduct for councillors should be altered to "remove unnecessary restrictions on councillors representing their constituents".

Revisions should also make a clearer distinction between private and official conduct, found the report.