The party's justice spokesman, Graeme Pearson, said such money should, as now, be spent helping communities ridden by crime rather than plug holes in the policing budget.
Mr Pearson, a former senior officer, was responding to news that the 2014-15 budget, for the first time in history, includes £6m seized under the Proceeds of Crime Act, or Poca.
His former colleagues, including Chief Constable Stephen House, have long argued in favour of a "gangster tax" that would use Poca to pay for policing. Two years ago he said he believed that Justice Secretary Kenny MacAskill was reluctant to allow such a move, saying he had a "mental block" on the issue.
Until now most Poca money has gone to finance the Scottish Government's CashBack for Communities scheme, which provides support for things like youth diversion projects. In 2012-13 some £12m was raised from Poca.
The proposed budget will formally go for approval to the Scottish Police Authority (SPA) tomorrow. Mr Pearson hopes the Poca element, already pioneered south of the border, will be rejected.
He said: "To 'pay' the police from criminal assets is wrong. It has created a bureaucracy in England of highly paid officials to decide who gets what. It has meant the government can leave gaps in budgets to be met from criminal money, it has created a perception that police will be motivated by profit and not justice.
"It finally ensures that the monies promised to the police and the Crown Office will not be returned to the poorest communities in the country.
"It is amoral, indefensible and wrong."
A spokesman for Polcie Scotland said no decision had been taken on how cash from Poca would be spent, but added: "It is anticipated that the monies will be used to support policing activities in communities."