The leader of Scotland's largest local authority has launched an outspoken attack on the election debacle.
Steven Purcell criticised the decision to hold two elections on one day
Glasgow City Council leader Steven Purcell said local authority and Holyrood elections must never again be held on the same day.
The news comes as Labour retained overall control of the council despite losing more than 20 seats.
Mr Purcell said that holding the two elections simultaneously had caused the large number of rejected ballot papers.
Labour retained its majority on the council, winning 45 seats out of 79. At the last election, Labour had 71 seats.
Mr Purcell said: "In a democracy it is absolutely vital that each and every vote is counted. There must be an investigation into what happened yesterday.
"It's surely not a coincidence that there were so many spoilt papers at the same time as a new electoral system was introduced. This is unacceptable.
"I know from local experience that many people were confused by the different systems.
"In future we must have council and parliament elections held separately and better information for voters."
Speaking about his own re-election, and Labour gaining a majority in Glasgow, Mr Purcell said he was delighted that citizens had backed his party.
He also said that Glasgow had now truly entered a new era of multi-party politics.
Labour returned 45 councillors, the SNP 22, the Greens and Liberal Democrat returned five each, and Solidarity and the Conservatives returned one apiece.
Mr Purcell added: "There are new homes, schools and leisure facilities and more jobs than ever before.
"We must now ensure that every Glaswegian can be part of this and that will be my top priority for the next four years.
"There is a new politics in Glasgow. This council looks very different from anything which has gone before and it's important all parties work together for the good of the city.
"Although Glasgow will be run by a Labour administration I will be looking at ways we can work productively with all councillors, regardless of their party allegiance."