Convicted criminals wait an average 14 months before they actually serve jail time, according to research by RTL news.
Leaked justice ministry figures show the official maximum of 30 days between sentencing and jail is often exceeded. This means people convicted of violence or sexual offences may be allowed back on the streets before going to prison, RTL news said.
After sentencing, the convicted criminal is sent a letter telling him or her when to report to jail. But this, the broadcaster said, can often be delayed by, for example, a planned holiday. If a criminal arrives at jail without ID, he or she will be turned away and a new legal procedure will begin.
RTL news said earlier some 15,000 people in the Netherlands have not yet served their jail sentences.
Junior justice minister Fred Teeven said in a reaction the figures in the document are preliminary and measures are already being taken to reduce the length of time it takes to send someone to jail.