He said Henderson normally took up to 11 remand prisoners at a time, however, there have been up to 23 in the cells over the last month.
"It's a burden on police staff - it's almost like a mini prison," he said.
"That puts the police under considerable pressure. It does create extra work. Staff aren't pulled off the street - but it could get to that."
On a normal weekend major metropolitan stations, such as Henderson and Counties Manukau, could house 20-30 people who had been arrested, he said.
"Then you have 25 bloody remands on top of that, when there's really only supposed to be 11. It's putting us under quite a bit of pressure.
"It happens often at this time of year ... the jails are absolutely chocka with remands ... but this time police have been told that it's not going to let up until May. Police usually say, 'Yeah, we'll look after them for a few weeks or a month', but until May? That's a long time.
"Police always help out, it's nothing new. Part of the deal we have is to take the overflow, but we're way over the numbers we should have."
Corrections footed the bill for housing and feeding remand prisoners and provided security guards to ensure a safe staff-to-inmate ratio. However the source said police still had to manage the prisoners.
Police National Headquarters was aware of the issue.
"We are continuing to work with the department as it manages the current situation to ensure the safety of remand prisoners and police staff," a spokesman said.
Corrections could not say how many remand prisoners were housed in police stations over the same period last year, but a spokeswoman said the figure was higher this year "by quite a bit". She would not give a breakdown of the figures for security reasons.
Corrections' National Commissioner Jeremy Lightfoot would not be drawn on why there was no space for the inmates in prison or when the issue would be resolved.
"It is normal for there to be a spike in the number of remand prisoners following the holiday period, however, this year the numbers are higher than forecast, particularly in the upper North Island."
Mr Lightfoot said Corrections staff worked closely with police to ensure there were cells available "if required" to hold remand prisoners until they could be placed in a prison cell.
What is a remand prisoner?
• Someone held in custody while they wait for their trial or sentencing.
• A remand prisoner could be held in police cells, court cells, psychiatric facilities or prison.
• About 20 per cent of the people in prison are on remand.
• People on remand are kept separate from sentenced prisoners, in units or wings only for remand prisoners.
• Any time spent on remand is taken off a person's total sentence time.
