A GOVERNMENT investigation has been launched into Bolton's council elections to discover why 10,000 people returned invalid votes.

Officials from the Electoral Commission and council chiefs will investigate the postal vote which resulted in 10,302 ballot papers being returned unsigned to the town hall.

The papers were considered "spoiled" and could not be counted in Thursday's poll which saw the Labour Party lose overall control of Bolton Council for the first time in 23 years.

The papers sent in without signatures could have had a decisive say in many of the town's wards where council seats were closely contested.

Officials from the Electoral Commission will now work with the local authority to produce a report on the postal ballot.

It will be published in July and will also examine voter confidence and security.

A total of 86,000 ballot papers, from Bolton's 206,000 voters, were mailed to the town hall in the borough's first all-out postal ballot

The ballot slips had to be signed to validate the vote but fears were raised in the run up to the election that voters did not understand instructions on the papers.

A similar postal vote in Trafford, where voters were not required to sign the paper, recorded just 414 spoils and a turnout of 52 per cent -- 10 per cent higher than Bolton.

Kevan Helsby, a former mayor and Labour councillor for Blackrod, was one of several candidates who narrowly lost out. In some wards up to 700 ballot papers were not able to be counted. Mr Helsby -- who lost his seat by 94 votes as 373 invalid papers were returned -- today criticised the postal vote election.

He said: "To have such huge numbers of invalid votes means that there is something seriously wrong with the electoral process. I'm disappointed about losing my seat but I have no plans to contest the result." But he added: "Overall for the election it is very disappointing -- the figures are far, far too high. This is not a satisfactory situation."

The election returning officer, Bernard Knight, Bolton Council's chief executive, admitted the amount of invalid votes was "disappointing". He said: "It's disappointing because people had gone to the trouble to fill in the ballot paper and their votes could not be counted. It is a pity that those 10,000 did not do what they should have done to make their vote count."

"It is possible that people found it hard to understand the instructions. Some people were unhappy about having to sign the papers and they felt that it was inappropriate."

But Mr Knight said the trial had been worthwhile despite costing more than £80,000. He added: "The turnout was up by 10 per cent and we can take some comfort from the fact that people were encouraged to take part."