No costs yet known for Vic prison land

Victoria plans to double the size of a maximum security prison precinct but hasn't yet bought the land or negotiated a price.

The Andrews government announced its intended expansion of the site at Lara, near Geelong, on Thursday but provided no details or costings.

"The costs and size of the expansion will be determined by the budget," Corrections Minister Gayle Tierney told reporters.

Ms Tierney said the size of the land needed had not yet been determined.

However she said the prison would be maximum security and approximately double the size of the current facility, which holds 450 beds.

"We are currently in negotiations with land owners to buy more land to expand the size of the prison complex," Ms Tierney said.

She said the government expected the prison population to significantly grow in coming years.

Opposition Leader Matthew Guy said the government needed to get serious about tackling crime.

"They might talking about a new prison but they certainly aren't changing the law to put people inside it," he said.