Such a move would show ministers are “serious” about ending homelessness, according to a joint statement signed by the Scottish Conservatives, Labour, the Greens and the Liberal Democrats.
The four opposition parties are calling on the Scottish Government to include the measure in its action plan on tackling homelessness, which is set to be published tomorrow.
It is expected to set out a five-year programme to address the issue of temporary accommodation in partnership with local councils and other organisations.
Last month a survey of 74 homeless people stuck in B&Bs across Scotland found that almost half had no access to a kitchen or cooking facilities, meaning they often had to skip meals.
The majority were also subjected to curfews and were not allowed to be visited by family or friends, the research published by homelessness charity Crisis found.
Earlier this year, an investigation by the Ferret website found that Scottish councils have spent more than £600 million on temporary accommodation for the homeless over the past five years.
The joint statement suggests changing the law so that homeless people are moved on from this kind of accommodation into more settled housing after one week.
It was signed by Scottish Tory housing spokesman Graham Simpson and his counterparts Andy Wightman of the Greens, Labour’s Pauline McNeill and Alex Cole-Hamilton of the Lib Dems.
“To end homelessness, we need a bold approach,” it read.
“We believe that legislating to place a time limit of seven days for the period someone is placed in unstable temporary accommodation will demonstrate to the Scottish people we are serious about achieving this goal for all homeless people.”
The joint statement was welcomed by Crisis chief executive Jon Sparkes, who said people in temporary accommodation were living “in limbo”.
“It is heartening that this has been recognised across the political divide and I welcome this cross-party approach to call for the issue to be tackled urgently,” he added.
Last year ministers put a seven-day cap on the length of time that homeless families and pregnant women could be housed in unsuitable accommodation.
Housing minister Kevin Stewart said: “While temporary accommodation provides an important safety net in emergency situations, we are clear it must be for as short a time as possible.”