Dozens of people were blocked from voting in a marginal seat after a "shambolic" mix-up over the electoral register, Labour officials said today.
Christine Russell, who is standing for re-election as Labour MP in Chester, said many constituents were turned away because they had not been included on an updated list of people entitled to vote.
She said it was thought people registered within the past month were affected.
"It was people who were legally registered to vote but who had not been included on the list at polling stations," she said.
"We are aware of it happening at at least six polling stations. We've had formal complaints from voters."
The seat, which Ms Russell won with a 915 majority in 2005, has been targeted by the Conservatives, with pundits suggesting the constituency was one of Labour's most vulnerable in the North West.
Ms Russell, who was first elected in 1997, estimated "dozens" of people were thwarted from voting.
"If someone had tried to vote on their way to work and were turned away, after a long day they were not going to go back later," she said.
"The clerks were trying to check the lists with the town hall but, by 1pm, you just couldn't get through on the phone.
"It's just a shambolic administration, a lack of preparation and a lack of training."
She said she would await the outcome of the election before considering any further action.
"We will wait to see what the results say," she said.
Cheshire West and Chester Council was unavailable for comment.
But a spokeswoman told the Chester Chronicle: "A handful of people turned up at the polling stations on Thursday morning and the staff on duty tried to ring the electoral office to check if they were on the register.
"Unfortunately, the phone line was engaged so the voters, some of whom were probably on their way to work, were reassured and advised to come back later in the day."