The Prison Officers' Association has stated that when more rioters are jailed, an emergency plan to prevent prison congestion may be activated in the next few days.

One possibility is to deploy Operation Early Dawn, a contingency that permits prisoners awaiting a court appearance to be detained in police cells until jail space becomes available.

Following the fatal stabbing of three girls in Southport, the government pledged swift sentencing for those participating in the riots, which resulted in hundreds of people appearing in UK courts.

But the POA's national chairman told BBC Radio 4's Broadcasting House programme this risked "clogging up prison cells".

Speaking on Sunday, Mark Fairhurst said he would not be "surprised" if the Ministry of Justice at some point on Monday morning announced that "Operation Early Dawn kicks into play at some point next week".

A Ministry of Justice spokesperson told the BBC it would "update on operational decisions in the normal way", adding that the government would "always make sure we have the prison places we need".

But keeping defendants waiting for a court appearance in police cells unless it is confirmed there is a prison bed available for them could delay court dates.

Mr Fairhurst warned that this had a "massive knock-on effect on the entire justice system" as police cells got clogged up, meaning officers had not "got the power to arrest people and put them away".

He said last week had seen 397 new receptions, the "biggest influx" he had seen for some time, and that on Friday, the adult male closed estate only had 340 spaces left.

Pressure on the prison system is "really, really tight", he warned, adding offenders could be sent hundreds of miles from home to serve a sentence in a prison with spaces.

Justice Secretary Shabana Mahmood announced plans to cut the proportion of the sentence inmates must serve behind bars from 50% to 40%.

The temporary move - which does not apply to those convicted of sex offences, terrorism, domestic abuse or some violent offences - is expected to result in 5,500 offenders being released in September and October.

Last week, the government confirmed those involved in recent unrest would not be excluded from its plans to release some inmates from jail early.

On Sunday, Cleveland Police said two women aged 24 and 52, had been charged with violent disorder, and Merseyside Police said a 47-year-old man had been charged with the same offence.

MPs have already approved the laws allowing the plan to be put into action and any changes could require updating the legislation in a short space of time if additional exemptions are to be included.

Operation Early Dawn was previously triggered by the Conservative government in May in a bid to tackle overcrowding in jails.