Public Security Minister Yitzhak Aharonovitch has ordered the police and prison service to prepare to detain hundreds of migrant workers likely to be arrested under a bill whose final Knesset readings were delayed Monday by a week.

The bill aims to deter migrant workers from crossing into Israel by making it possible to jail those caught staying here for long periods without being tried or expelled.

Migrant workers already here could be jailed for the most minor offense such as spraying graffiti or stealing a bicycle - infractions for which they wouldn't have been detained before. They could be held for anywhere from three years to life.

The bill would amend the Prevention of Infiltration Law of 1954, which was passed to prevent the entry of hostile elements or Palestinian refugees into Israel but doesn't address migrant workers or asylum seekers. The Entry Law forbids the jailing of anyone for more than 60 days if he cannot be expelled from the country.

According to the Population and Immigration Authority, a record 2,931 people infiltrated the border in December for a total of 16,816 in 2011. Since 2005, more than 54,000 people seeking work or asylum have crossed into Israel illegally.

Under the bill, migrant workers caught at the border could be held in detention for up to three years, assuming they are not expelled. Detainees who previously were entitled to be brought before a judge within 96 hours of arrest could be held for 14 days without a hearing.

The bill also allows criminal charges against any suspect illegal migrant or asylum seeker, or anyone who aids one or gives one shelter.

At a meeting earlier this week, the prison service, the police and the justice and interior ministries told Aharonovitch about the progress being made in enlarging the Saharonim detention facility to accommodate 700 more prisoners.

If necessary, a few hundred prisoners could be housed in the adjacent Ketziot prison, where beds have been vacated by prisoners exchanged for abducted soldier Gilad Shalit.

The police will first focus on migrants from South Sudan, after Prime Minister Benjamin Netanyahu spoke to the South Sudanese president about ways to return migrants there now that the situation in the newly independent country has improved.

Prison service officials said those most likely to be held for criminal acts are relatively young and unattached, so few children would have to be detained with their parents. Still, Saharonim is ready to take in children if necessary.

The Public Security Ministry said it was not planning wholesale arrests; this would be a focused campaign aimed at around 1,000 people.

"Once again the government is lying to the public. Even before the law has been passed, the government is proving its true intentions regarding the punishments set down," said Reut Michaeli, the director of the Hotline for Migrant Workers.

"The result is that in Israel refugees can be punished with life imprisonment - which is disproportionate to the seriousness of their crime or the degree any other person in the same circumstances would be punished."