A council blunder could lead to a mobile phone mast being built near homes in Cambridge despite objections from residents.
The council's rejection letter arrived one day late
The city council rejected proposals by phone company O2 to build the 11-metre high mast on Queen Edith's Way.
But its letter to O2 opposing the planning application arrived one day after the 56-day deadline.
O2 has pledged to go ahead with the mast but a manager said he would be meeting with residents.
On Thursday, the BBC News website contacted Cambridge City Council but no comment was provided.
Queen Edith's ward Liberal Democrat councillor Geoffrey Heathcock has called for an investigation into the cause of the error.
"These were pretty serious mistakes and to say in a letter 'sorry folks, nothing we can do' is not good enough," he added.
Protestors are appealing to the company to find an alternative location for the mast.
One resident, Andrew Sharkey, said: "Using this technicality of a one day late decision is not the way for a company to proceed in this day and age, ignoring the wishes of its residents and customers."
Mr Sharkey's wife Tess said: "I'm going to have an 11-metre mast just 10 metres from my son's head."
O2's community relations manager James Stevenson said the company hoped to meet the local community but would go-ahead with the phone mast.
"They (Cambridge City Council) had 56 days in which to decide whether we could have (planning permission) and they took longer than the 56 days to come back to us," he added.
"We assumed that they weren't bothered about it, which is the case with most planning authorities.
"People are a bit upset about it and I'm going to see them next week."