A London mayoral candidate has made a formal complaint after council bungling meant many voters were turned away from the ballot box.
Names were missing from polling lists across Barnet and residents attempting to cast their vote were stopped.
The council has apologised and said updated registers should be in place at stations by 10am.
But Sophie Walker, the Women's Equality Party mayoral candidate, has registered a complaint with the council, along with the London Assembly.
She told the Press Association: "I am very disappointed. I have spent my morning responding to messages from people upset that they could not vote.
"Women first got the vote 100 years ago and there are women today who have been unable to vote."
Ms Walker, who will be voting in Barnet later, added: "These are vital votes, particularly for smaller parties.
"We will be pursuing a complaint."
Guy Fryer, head of stage at the Lyric Theatre in Hammersmith, was missing from the list but managed to vote after "standing his ground" at a polling station in Strawberry Vale.
He said: "How can we have a fair vote if not everyone has voted?
"An apology is really not good enough.
"It's not a bring-and-buy sale. It really, really matters."
Journalist Jennifer Lipman, who attempted to vote at Hoop Lane polling station, said the problem was "disastrous".
"We had our ballot papers and they checked their lists, but we were not on there," she said. "They advised us to call the helpline but had no further information.
"It's incredibly frustrating because even if they sort the problem, there will be plenty of people who are unable to vote later in the day, not to mention the likelihood of large queues building up.
"I firmly believe in the right to vote so I am upset to seemingly be denied it."
A Barnet Council spokesman: "We are aware of problems with our electoral registration lists this morning at polling stations in Barnet which have meant that a number of people who had not brought their polling card with them were unable to vote.
"We are working to resolve this issue and the updated registers have been sent to all the polling stations, which we expect to be in place by 10am. In the meantime, people who have their polling cards with them are able to vote.
"We are advising residents to bring their polling cards. If people were unable to vote this morning they are being advised to return if possible later before the stations close at 10pm. We apologise for the problems."
Zac Goldsmith's team appealed to voters turned away from polling stations to return later.
A spokesman for the Tory mayoral candidate said: "There has clearly been a major problem across the whole of the borough of Barnet that has resulted in properly registered voters being turned away.
"As we speak, the problem has not yet been rectified although we understand that the local Returning Officer is belatedly reprinting registers and it remains to be seen what the effect of this will be upon the three ballots taking place there.
"We would strongly encourage any voters wrongly turned away to return to their polling stations at any time up to 10pm this evening if at all possible."